Blank mask and photomask using the same

ABSTRACT

A blank mask including a transparent substrate, a phase shift film disposed on the transparent substrate, and a light shielding film disposed on the phase shift film. The phase shift film has XRD maximum peak at 2θ of 15° to 30° when normal mode XRD analysis is performed on an upper surface of the phase shift film. The transparent substrate has XRD maximum peak at 2θ of 15° to 30° when performing normal mode XRD analysis on a lower surface of the transparent substrate. AI1 value of the blank mask expressed by below Equation is 0.9 to 1.1.AI⁢⁢1=XM⁢⁢1XQ⁢⁢1XM1 is the maximum value of the measured X-ray intensity when the normal mode XRD analysis is performed on upper surface of the phase shift film. XQ1 is the maximum value of the measured X-ray intensity when the normal mode XRD analysis is performed on the lower surface of the transparent substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(a) of KoreanPatent Application No. 10-2021-0041895 filed on Mar. 31, 2021, No.10-2021-0025946 filed on Feb. 25, 2021, No. 10-2020-0189912 filed onDec. 31, 2020, and No. 10-2021-0019157 filed on Feb. 10, 2021, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The present disclosure relates to a blank mask and a photomask using thesame.

2. Description of Related Art

Due to high integration of semiconductor devices or the like,miniaturization of circuit patterns of semiconductor devices is beingrequired. For this reason, the importance of a lithography technique,which is a technique for developing a circuit pattern on a wafer surfaceusing a photomask is being further emphasized.

For developing a miniaturized circuit pattern, an exposure light used inan exposure process (photolithography) is required to have a shortenedwavelength. As the exposure light used recently, there is ArF excimerlaser (wavelength of 193 nm) or the like.

On the other hand, there are Binary mask, Phase shift mask, and the likeas photomasks.

The Binary mask has a structure in which a light shielding pattern filmis formed on a transparent substrate. In a surface where a lightshielding pattern film is formed from the Binary mask, a transmissiveportion not including a light shielding pattern film allows exposurelight to be transmitted, and a light shielding portion including a lightshielding pattern film shields exposure light to transfer a pattern on aresist film of the surface of a wafer. However, the Binary mask maycause a problem in the development of a minute pattern due todiffraction of light occurring at the edge of the transmissive portionas the pattern is being more miniatured.

As a phase shift mask, there are Levenson type, Outrigger type, andHalf-tone type. Among the above, Half-tone type phase shift mask has astructure in which a pattern formed with semi-transmissive films isformed on a transparent substrate. In a surface where a pattern isformed from the Half-tone type phase shift mask, a transmissive portionnot including a semi-transmissive film allows exposure light to betransmitted, and a semi-transmissive portion including asemi-transmissive layer allows attenuated exposure light to betransmitted. The attenuated exposure light is allowed to have a phasedifference compared to exposure light which has transmitted thetransmissive portion. Accordingly, diffraction light occurring at theedge of the transmissive portion is counteracted by the exposure lightwhich has transmitted the semi-transmissive portion, and thereby thephase shift mask can form a further refined minute pattern on thesurface of a wafer.

As related prior arts, there are Korean Patent Registration No.10-1360540, US Patent Publication No. 2004-0115537 and Japanese PatentPublication No. 2018-054836.

SUMMARY

A blank mask according to an embodiment includes a transparentsubstrate; a phase shift film disposed on the transparent substrate; anda light shielding film disposed on the phase shift film.

The blank mask is analyzed by normal mode XRD (X-Ray Diffraction).

When the normal mode XRD analysis is performed on an upper surface ofthe phase shift film, the phase shift film has a XRD maximum peak at 2θof 15° to 30°.

When the normal mode XRD analysis is performed on a lower surface of thetransparent substrate, the transparent substrate has a XRD maximum peakat 2θ of 15° to 30°.

The blank mask has an AI1 value of 0.9 to 1.1 expressed by Equation 1below.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Equation 1, the XM1 is the maximum value of the measured X-rayintensity when the normal mode XRD analysis is performed on the uppersurface of the phase shift film.

The XQ1 is the maximum value of the measured X-ray intensity when thenormal mode XRD analysis is performed on the lower surface of thetransparent substrate.

The blank mask may be analyzed by fixed mode XRD.

When the fixed mode XRD analysis is performed on the upper surface ofthe phase shift film, the phase shift film may have the first peak,which is the XRD maximum peak at 2θ of 15° to 25°.

When the fixed mode XRD analysis is performed on the lower surface ofthe transparent substrate, the transparent substrate may have the secondpeak, which is the XRD maximum peak at 2θ of 15° to 25°.

The blank mask may have an AI2 value of 0.9 to 1.1 expressed by Equation2 below.

$\begin{matrix}{{{AI}\; 2} = \frac{{XM}\; 2}{{XQ}\; 2}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the Equation 2, the XM2 is an intensity value of the first peak, andXQ2 is an intensity value of the second peak.

The blank mask may have an AI3 value of 0.9 to 1.1 expressed by Equation3 below.

$\begin{matrix}{{{AI}\; 3} = \frac{{AM}\; 3}{{AQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In the Equation 3, the AM1 is an area of a region where 2θ is 15° to 30°in an X-ray intensity graph measured when normal mode XRD analysis isperformed on the upper surface of the phase shift film.

The AQ1 is an area of a region where 2θ is 15° to 30° in an X-rayintensity graph measured when normal mode XRD analysis is performed onthe lower surface of the transparent substrate.

The blank mask may have an AI4 value of 0.9 to 1.1 expressed by Equation4 below.

$\begin{matrix}{{{AI}\; 4} = \frac{{XM}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In the Equation 4, the XM4 is the X-ray intensity where 2θ is 43° whenthe normal mode XRD analysis performed on the upper surface of the phaseshift film.

The XQ4 is the X-ray intensity where 2θ is 43° when the normal mode XRDanalysis performed on the lower surface of the transparent substrate.

When normal mode XRD analysis is performed on a light shielding film,the light film may have a maximum X-ray intensity value where 2θ is 15°to 30°.

When the XRD analysis is performed on the lower surface of thetransparent substrate, the light film may have a maximum X-ray intensityvalue where 2θ is 15° to 30°.

The blank mask may have an AI5 value of 0.9 to 0.97 expressed byEquation 5 below.

$\begin{matrix}{{{AI}\; 5} = \frac{{XC}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the Equation 5, the XC1 is the maximum value of the X-ray intensitymeasured on the upper surface of the light shielding film.

The XQ1 is the maximum value of the X-ray intensity measured on thelower surface of the transparent substrate.

The blank mask may have an AI6 value of 1.05 to 1.4 expressed byEquation 6 below.

$\begin{matrix}{{{AI}\; 6} = \frac{{XC}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In the Equation 6, the XC4 is the X-ray intensity where 2θ is 43° whenthe normal mode XRD analysis is performed on the upper surface of thelight shielding film.

The XQ4 is the X-ray intensity where 2θ is 43° when the normal mode XRDanalysis is performed on the lower surface of the transparent substrate.

In the blank mask, when PE₁ is 1.5 eV and PE₂ is 3 eV, the photon energyof incident light at the point where the Del_1 value according toEquation 7 below is 0 may be 1.8 to 2.14 eV.

$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta PE}\rightarrow 0}\left( \frac{\Delta DPS}{\Delta PE} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

In the Equation 7, when the phase shift film is measured with aspectroscopic ellipsometer by applying an incident angle of 64.5°, theDPS value is the phase difference between the P wave and the S wave ifthe phase difference between the P wave and the S wave of the reflectedlight is 180° or less, or a value obtained by subtracting the phasedifference between the P wave and the S wave from 360° if the phasedifference between the P wave and the S wave of the reflected light ismore than 180°.

The PE value is the photon energy of the incident light within the rangeof the PE₁ value to the PE₂ value.

In the blank mask, when the PE₁ value is 3.0 eV and the PE₂ value is 5.0eV, the photon energy of incident light at the point where the Del_1value is 0 may be 3.8 to 4.64 eV.

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is aminimum value within photon energy values of incident light at a pointwhere the Del_1 value is 0, the average value of the Del_1 may be 78 to98°/eV.

In the blank mask, when the PE₁ value is the minimum value within photonenergy values of the incident light at the point where the Del_1 valueis 0, and the PE₂ value is the maximum value within the photon energyvalues of the incident light at the point where the Del_1 value is 0, anaverage value of the Del_1 may be −65 to −55°/eV.

In the blank mask, when the PE₁ value is the maximum value within photonenergy values of incident light at the point where the Del_1 value is 0and the PE₂ value is 5.0 eV, the average value of the Del_1 may be 60 to120°/eV.

The blank mask may have a maximum value of the Del_1 value of 105 to300°/eV when the PE₁ value is 1.5 eV and the PE₂ value is 5.0 eV, the

The blank mask may have a photon energy of the incident light of 4.5 eVor more at a point where the Del_1 value has the maximum value.

The phase shift film may include a phase difference adjustment layer anda protective layer disposed on the phase difference adjustment layer.

The phase shift film may include a transition metal, silicon, oxygen,and nitrogen.

The phase difference adjustment layer may include nitrogen in an amountof 40 to 60 atom %.

The protective layer may include nitrogen in an amount of 2θ to 40 atom%.

The protective layer may include a region in which a ratio of nitrogencontent to oxygen content is 0.4 to 2 in the thickness direction.

The region may have a thickness of 30 to 80% compared to a totalthickness of the protective layer.

A blank mask according to another embodiment includes a transparentsubstrate; a phase shift film disposed on the transparent substrate; anda light shielding film disposed on the phase shift film.

The blank mask may have a photon energy of the incident light at thepoint where Del_1 is 0 expressed by Equation 7 below of 3.8 to 4.64 eVwhen the PE₁ value is 3.0 eV and the PE₂ value is 5.0 eV.

$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta PE}\rightarrow 0}\left( \frac{\Delta DPS}{\Delta PE} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

In the Equation 7, the DPS value is, when the light shielding film isremoved from the blank mask and after that the surface of the phaseshift film is measured with a spectroscopic ellipsometer by applying anincident angle of 64.5°, the phase difference between the P wave and theS wave if the phase difference between the P wave and the S wave is 180°or less, or a value obtained by subtracting the phase difference betweenthe P wave and the S wave from 360° if the phase difference between theP wave and the S wave of the reflected light is more than 180°.

The PE value is the photon energy of the incident light within the rangeof PE₁ to PE₂.

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is 3.0eV, the photon energy of the incident light at the point where the Del_1value is 0 may be 1.8 to 2.14 eV.

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is aminimum value within photon energy values of incident light at a pointwhere the Del_1 value is 0, the average value of the Del _1 is 78 to98°/eV.

In the blank mask, when the PE₁ value is the minimum value within photonenergy values of the incident light at the point where the Del_1 valueis 0 and the PE₂ value is the maximum value within the photon energyvalues of the incident light at the point where the Del_1 value is 0, anaverage value of the Del_1 may be −65 to −55°/eV.

In the blank mask, when the PE₁ value is the maximum value within photonenergy values of incident light at the point where the Del_1 value is 0and the PE₂ value is 5.0 eV, the average value of the Del_1 may be 60 to120°/eV.

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is 5.0eV, the maximum value of the Del_1 may be 105 to 300°/eV.

The blank mask may have a photon energy of the incident light of 4.5 eVor more at a point having the maximum value of the Del_1.

The blank mask may be analyzed by normal mode XRD.

When the normal mode XRD analysis is performed on the upper surface ofthe phase shift film, the phase shift film may have the XRD maximum peakat 2θ of 15° to 30°.

When the normal mode XRD analysis is performed on the lower surface ofthe transparent substrate, the transparent substrate may have the XRDmaximum peak at 2θ of 15° to 30°.

The blank mask may have an AI1 value of 0.9 to 1.1 expressed by Equation1 below.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the Equation 1, the XM1 is the maximum value of the X-ray intensitymeasured when the normal mode XRD analysis is performed on the uppersurface of the phase shift film.

The XQ1 is the maximum value of the X-ray intensity measured when thenormal mode XRD analysis is performed on the lower surface of thetransparent substrate.

The blank mask may be analyzed by fixed mode XRD.

When the fixed mode XRD analysis is performed on the upper surface ofthe phase shift film, the first peak, which is the maximum peak of theX-ray intensity measured may be located at 2θ of 15° to 25°.

When the fixed mode XRD analysis is performed on the lower surface ofthe transparent substrate, the second peak, which is the maximum peak ofthe X-ray intensity measured may be located at 2θ of 15° to 25°.

The blank mask may have an AI2 value of 0.9 to 1.1 expressed by Equation2 below.

$\begin{matrix}{{{AI}\; 2} = \frac{{XM}\; 2}{{XQ}\; 2}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the Equation 2, the XM2 is the intensity value of the first peak, andthe XQ2 is the intensity value of the second peak.

In an embodiment, the photomask may have an AI3 value of 0.9 to 1.1expressed by Equation 3 below.

$\begin{matrix}{{{AI}\; 3} = \frac{{AM}\; 3}{{AQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In the Equation 3, the AM1 is an area of a region where 2θ is between15° and 30° in an X-ray intensity graph measured when normal mode XRDanalysis is performed on the upper surface of the phase shift film.

The AQ1 is an area of a region where 2θ is between 15° and 30° in anX-ray intensity graph measured when normal mode XRD analysis isperformed on the lower surface of the transparent substrate.

In an embodiment, the photomask may have an AI4 value of 0.9 to 1.1expressed by Equation 4 below.

$\begin{matrix}{{{AI}\; 4} = \frac{{XM}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In the Equation 4, the XM4 is the X-ray intensity where 2θ is 43° whenthe normal mode XRD analysis performed on the upper surface of the phaseshift film.

The XQ4 is the X-ray intensity where 2θ is 43° when the normal mode XRDanalysis performed on the lower surface of the transparent substrate.

When normal mode XRD analysis is performed on the upper surface of thelight shielding film, the light shielding film may have the maximumvalue of the X-ray intensity where 2θ is 15° to 30°.

When the XRD analysis is performed through the lower surface of thetransparent substrate, the transparent substrate may have a maximumvalue of the X-ray intensity where 2θ is 15° to 30°.

The blank mask may have an AI5 value of 0.9 to 0.97 expressed byEquation 5 below.

$\begin{matrix}{{{AI}\; 5} = \frac{{XC}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the Equation 5, the XC1 is the maximum value of the X-ray intensitymeasured on the upper surface of the light shielding film.

The XQ1 is the maximum value of the X-ray intensity measured on thelower surface of the transparent substrate.

The blank mask may have an AI6 value of 1.05 to 1.4 expressed byEquation 6 below.

$\begin{matrix}{{{AI}\; 6} = \frac{{XC}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In the Equation 6, the XC4 is the X-ray intensity where 2θ is 43° whenthe normal mode XRD analysis performed on the upper surface of the lightshielding film.

The XQ4 is the X-ray intensity where 2θ is 43° when the normal mode XRDanalysis performed on the lower surface of the transparent substrate.

The phase shift film may include a phase difference adjustment layer anda protective layer disposed on the phase difference adjustment layer.

The phase shift film may include a transition metal, silicon, oxygen,and nitrogen.

The phase difference adjustment layer may include nitrogen in an amountof 40 to 60 atom %.

The protective layer may include nitrogen in an amount of 2θ to 40 atom%.

The protective layer may include a region in which a ratio of nitrogencontent to oxygen content is 0.4 to 2 in the thickness direction.

The region may have a thickness of 30 to 80% compared to a totalthickness of the protective layer.

A photomask according to another embodiment includes a transparentsubstrate; a phase shift film disposed on the transparent substrate; anda light shielding film disposed on at least some of the phase shiftfilm.

The photomask is analyzed by normal mode XRD.

When the normal mode XRD analysis is performed on the upper surface ofthe phase shift film, the maximum peak of the X-ray intensity measuredis located at 2θ of 15° to 30°.

When the normal mode XRD analysis is performed on the lower surface ofthe transparent substrate, the maximum peak of the X-ray intensitymeasured is located at 2θ of 15° to 30°.

The AI1 value expressed by the Equation 1 below is 0.9 to 1.1.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the Equation 1, the XM1 is the maximum value of the X-ray intensitymeasured when the normal mode XRD analysis is performed on the uppersurface of the phase shift film.

The XQ1 is the maximum value of the X-ray intensity measured when thenormal mode XRD analysis is performed on the lower surface of thetransparent substrate.

A photomask according to another embodiment includes a transparentsubstrate; a phase shift film disposed on the transparent substrate; anda light shielding film disposed on the phase shift film.

When the PE₁ value is 3.0 eV and the PE₂ value is 5.0 eV, the photonenergy of the incident light at the point where Del_2 is 0 expressed byEquation 8 below is 3.8 to 4.64 eV.

$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta\;{PE}}\rightarrow 0}\left( \frac{\Delta\;{DPS}}{\Delta\;{PE}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

In the Equation 8, the DPS value is, when the light shielding film isremoved and after that the phase shift film is measured with aspectroscopic ellipsometer by applying an incident angle of 64.5°, theDPS value is the phase difference between the P wave and the S wave ifthe phase difference between the P wave and the S wave of the reflectedlight is 180° or less, or a value obtained by subtracting the phasedifference between the P wave and the S wave from 360° if the phasedifference between the P wave and the S wave of the reflected light ismore than 180°.

The PE value is the photon energy of the incident light within the rangeof PE₁ to PE₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view for illustrating a blank mask according toone embodiment;

FIG. 2 is a schematic view for illustrating a process of normal mode XRDanalysis;

FIG. 3 is a conceptual view for illustrating an X ray intensity measuredby performing normal mode XRD analysis to a phase shift film in a blankmask according to an embodiment;

FIG. 4 is a conceptual view for illustrating an X ray intensity measuredby performing normal mode XRD analysis to a transparent substrate in ablank mask according to an embodiment;

FIG. 5 is a schematic view for illustrating a process of fixed mode XRDanalysis;

FIG. 6 is a conceptual view for illustrating an X ray intensity measuredby performing fixed mode XRD analysis to a phase shift film in a blankmask according to one embodiment;

FIG. 7 is a conceptual view for illustrating an X ray intensity measuredby performing fixed mode XRD analysis to a transparent substrate in ablank mask according to one embodiment;

FIG. 8 is a conceptual view for illustrating an X ray intensity measuredby performing fixed mode XRD analysis by performing normal mode XRDanalysis to a light shielding film in a blank mask according to anembodiment; and

FIG. 9 is a sectional view for illustrating a blank mask according toanother embodiment;

FIG. 10 is a conceptual view for showing principle for measuring a phasedifference of P wave and S wave of reflected light of a phase shiftfilm;

FIG. 11 is a sectional view for illustrating a photomask according toanother embodiment;

FIG. 12 is a graph of measuring distribution of DPS value depending onPhoton energy of incident light of Examples 4;

FIG. 13 is a graph of measuring distribution of Del_2 value depending onPhoton energy of incident light of Example 4;

FIG. 14 is a graph of measuring distribution of DPS value depending onPhoton energy of incident light of Examples 5;

FIG. 15 is a graph of measuring distribution of Del_2 value depending onPhoton energy of incident light of Example 5;

FIG. 16 is a graph of measuring distribution of DPS value depending onPhoton energy of incident light of Examples 6;

FIG. 17 is a graph of measuring distribution of Del_2 value depending onPhoton energy of incident light of Example 6;

FIG. 18 is a graph of measuring distribution of DPS value depending onPhoton energy of incident light of Comparative Examples 3;

FIG. 19 is a graph of measuring distribution of Del_2 value depending onPhoton energy of incident light of Comparative Examples 3;

FIG. 20 is a graph of measuring distribution of DPS value depending onPhoton energy of incident light of Comparative Examples 4; and

FIG. 21 is a graph of measuring distribution of Del_2 value depending onPhoton energy of incident light of Comparative Examples 4.

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings so thatthey can be easily practiced by those skilled in the art to which thepresent application pertains. However, the example embodiments may beembodied in many different forms and is not to be construed as beinglimited to the embodiments set forth herein.

In this application, the term for degree like “about”, “substantially”and the like is used for meaning values approximative from/to the valuewhen a tolerance proper to referred meaning for manufacture andsubstance is presented. Additionally, these terms for degree are used tohelp understanding of example embodiments and to prevent that anunconscionable trespasser unjustly uses the presented content in whichexact or absolute number is referred.

Throughout this application, the phrase “combination(s) thereof”included in a Markush-type expression denotes one or more mixtures orcombinations selected from the group consisting of components stated inthe Markush-type expression, that is, denotes one or more componentsselected from the group consisting of the components are included.

Throughout this application, the description of “A and/or B” means “A,B, or A and B.”

Throughout this application, terms such as “first”, “second”, “A”, or“B” are used to distinguish the same terms from each other unlessspecially stated otherwise.

In this application, “B being placed on A” means that B is placed indirect contact with A or placed over A with another layer or structureinterposed therebetween and thus should not be interpreted as beinglimited to B being placed in direct contact with A.

In this application, a singular form is contextually interpreted asincluding a plural form as well as a singular form unless speciallystated otherwise.

In this application, drawings are disclosed for illustration of exampleembodiments, some thereof may be expressed by being exaggerated oromitted, and the drawings are not expressed according to a reducedscale.

In this application, the transmissive portion (TA) means a region on thesurface of the photomask, which does not include a phase shift film andthereby transmits exposure light, and the semi-transmissive portion(NTA) means a region including the phase shift film and therebytransmits the attenuated exposure light (refer to FIG. 11).

A manufacturing process of a semiconductor device comprises a process offorming a designed pattern by forming a pattern on a semiconductor waferthrough an exposure process. In detail, when a photomask comprising adesigned pattern is disposed on a semiconductor wafer having a resistfilm applied to the surface thereof and then resist film is exposedthrough a light source, the resist film of the semiconductor wafer formsa designed resist pattern after treatment with a developing solution.

As semiconductors are highly integrated, more miniaturized circuitpatterns are required. In order to form a miniaturized pattern on asemiconductor wafer, exposure light having a shorter wavelength thanconventional exposure light may be applied. The exposure light forforming the miniaturized pattern comprises, for example, an ArF excimerlaser (wavelength of 193 nm).

As circuit patterns become more miniaturized, films comprised in thephotomask to form patterns are required to have improved opticalproperties.

In addition, a light source that generates exposure light having a shortwavelength may require high optical power. Such a light source mayincrease the temperature of the photomask comprised in the semiconductordevice manufacturing apparatus applied to exposure process.

The films comprised in the photomask to form the pattern may exhibit acharacteristic in which physical properties such as thickness and heightchange according to temperature change. Films comprised in the photomaskto form a pattern are required to have further reduced thermal variationcharacteristics.

The photomask may be formed by patterning a blank mask. Accordingly, thecharacteristics of the blank mask may affect the properties of thephotomask. Also, in some cases, oxidation treatment, heat treatment, andthe like are applied to a film of the blank mask during themanufacturing process of the blank mask, so that there is a differencebetween the characteristics of the film itself in the blank maskimmediately after the film formation and the characteristics of the thinfilm in the completed blank mask.

Crystal characteristics of each layer comprised in the blank mask may beappropriately adjusted so that optical properties and thermal propertiesof each layer comprised in the blank mask may be improved.

The inventors of the present disclosure ascertained the follows throughexperiments and completed the example embodiments; it can besubstantially suppressed that the degradation of resolution of aphotomask caused from temperature increase due to a light sourcegenerating a exposure light with a short wavelength, or the differencein optical properties between respective films, by adjusting the crystalcharacteristics of the films comprised in the blank mask.

Hereinafter, example embodiments will be described in further detail.

FIG. 1 is a sectional view for illustrating a blank mask according toone embodiment. The embodiment is described with reference to the FIG.1.

The blank mask 100 comprises a transparent substrate 10, a phase shiftfilm 20 disposed on the transparent substrate 10, and a light shieldinglayer 30 disposed on the phase shift film 20.

The material of the transparent substrate 10 is not limited as long asit has light transmittance to exposure light and can be applied to thephotomask. Specifically, the transmittance of the transparent substrate10 with respect to exposure light having a wavelength of 200 nm or lessmay be 85% or more. The transmittance may be 87% or more. Thetransmittance of the transparent substrate 10 with respect to ArF lightmay be 85% or more. The transmittance may be 87% or more. For example,the transparent substrate 10 may be a synthetic quartz substrate. Insuch a case, the transparent substrate 10 may suppress attenuation oflight transmitting the transparent substrate 10.

In addition, the transparent substrate 10 may reduce the occurrence ofoptical distortion by adjusting surface characteristics such as flatnessand roughness.

The phase shift film 20 may be disposed on an upper surface of thetransparent substrate 10.

In the blank mask 100, the light shielding film 30 is disposed on thephase shift film. The light shielding layer 30 may be used as an etchingmask for the phase shift film 20 when the phase shift film 20 is etchedin a pattern shape. In addition, the light shielding film 30 may blocktransmission of the exposure light incident from the rear side of thetransparent substrate 10.

Crystalline Properties of Phase Shift Film

A blank mask according to an embodiment comprises a transparentsubstrate; a phase shift film disposed on the transparent substrate; anda light shielding film disposed on at least some of the phase shiftfilm.

The blank mask is analyzed by normal mode XRD (X-Ray Diffraction).

When the normal mode XRD analysis is performed on an upper surface ofthe phase shift film, the phase shift film has the XRD maximum peak at2θ 15° to 30°.

When the normal mode XRD analysis is performed on a lower surface of thetransparent substrate, the transparent substrate has the maximum peak at2θ of 15° to 30°.

The AI1 value expressed by the Equation 1 below is 0.9 to 1.1.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the Equation 1, the XM1 is the maximum value of the measured X-rayintensity when the normal mode XRD analysis is performed on the uppersurface of the phase shift film, and the XQ1 is the maximum value ofmeasured X ray intensity when the normal mode XRD analysis is performedon the lower surface of the transparent substrate.

The optical properties of the phase shift film 20 are determineddepending on various factors such as a composition of elementsconstituting the phase shift film 20, a film density, and a filmthickness. Therefore, in order to maximize the resolution of the patternto be developed on the semiconductor wafer, the phase shift film 20 isdesigned and then formed in consideration of the above factors.

Meanwhile, the temperature of the phase shift film 20 may increase dueto heat generated from the light source during the exposure process, andthe thickness value, stress, and the like of the phase shift film 20 mayvary due to the heat.

For the thermal variation characteristics, the phase shift film 20 andthe transparent substrate 10 may have different characteristics. This isconsidered to be because it is different from the transparent substrate10 in the type of element, the content of each element, and the crystalstructure comprised in the phase shift film 20. Such a difference may bea factor causing a decrease in resolution of the photomask. In detail,in repetitive exposure processes for long duration, the transparentsubstrate 10 and the phase shift film 20 may exhibit differentdimensional variations and stress variations. For this reason,distortion of the optical path may occur, particularly at the interfacebetween the transparent substrate 10 and the phase shift film 20.

The embodiment may reduce the optical distortion occurring at theinterface between the transparent substrate 10 and the phase shift film20 by controlling the crystal characteristics of the phase shift film 20to be more similar to that of the transparent substrate 10.

By controlling factors such as the type of element constituting thephase shift film 20, the content of each element, the magnetic fieldstrength in the sputtering process, the substrate rotation speed, thevoltage applied to the target, the atmospheric gas composition, thesputtering temperature, and the conditions during the post-processingprocess, crystal characteristics of the phase shift film 20 may beadjusted.

In particular, the embodiment allows the plasma to be distributed overthe entire surface of the target in the chamber by disposing a magnet inthe sputtering equipment and forming a magnetic field when the phaseshift film 20 is formed using the sputtering equipment. By controllingthe distribution and strength of the magnetic field, it is possible tocontrol the crystal characteristics of the phase shift film formed withsputtering equipment.

FIG. 2 is a schematic view for illustrating a process of normal mode XRDanalysis. An embodiment will be described with reference to FIG. 2.

Crystal characteristics of the phase shift film and the transparentsubstrate may be analyzed by X-ray diffraction (XRD) analysis.

Before XRD analysis is performed, the light shielding film disposed onthe phase shift film is required to removed. When another film is placedbetween the phase shift film and the light shielding film, the otherfilm is also required to removed. That is, the light shielding film isremoved to expose the upper surface of the phase shift film. As a methodof removing the thin film, etching may be exemplarily applied.

XRD analysis can be run in normal mode. The normal mode XRD analysis isin θ-2θ mode. In the normal mode XRD analysis, X-rays generated from theX-ray generator 60 are emitted to the sample 80, and the X-raysreflected from the sample 80 are detected through a detector 70.

At this time, the X-ray generator 60 emits X-rays to the sample 80 at apredetermined incident angle θ. The incident angle θ is an angle betweenthe direction of the X-ray emitted from the X-ray generator 60 and thehorizontal plane of the sample 80. In addition, the X-ray generator 60emits X-rays to the sample 80 while changing the incident angle θ.

The detector 70 is disposed opposite to the location where the X-raygenerator 60 is disposed based on the location where the X-rays areincident in a surface of the sample 80. Also, the detector 70 detectsX-rays having a predetermined emission angle θ among the X-raysreflected from the sample 80. The emission angle θ is the angle betweenthe direction of the X-ray reflected from the sample 80 and thehorizontal plane of the sample 80.

In addition, the detector 70 moves in response to the scan direction ofthe X-ray generator 60. That is, when the X-ray generator 60 scans thesample 80, the detector 70 moves so that the incident angle θ and theemission angle θ are equal to each other. In the normal mode XRDanalysis, the X-ray generator 60 and the detector 70 may move on thesame plane so that the incident angle θ and the emission angle θ areequal to each other. In addition, the X-ray generator 60 may move sothat the distance from the position where the X-rays of the sample 80 isincident is constant. In addition, the detector 70 may move so that thedistance from the position where the X-rays of the sample 80 arereflected is constant. That is, the X-ray generator 60 and the detector70 may be moved while drawing an arc.

In normal mode XRD analysis, an X-ray source may be a copper (Cu)target. In normal mode XRD analysis, the wavelength of X-rays may beabout 1.542 nm. In normal mode XRD analysis, the voltage used togenerate X-rays may be about 45 kV. In normal mode XRD analysis, theelectric current used to generate X-rays may be about 200 mA. In normalmode XRD analysis, the measurement range of 2θ may be from about 10° toabout 100°. Normal mode XRD analysis can perform measurements at alltimes when the 2θ is changed by 0.05°. In normal mode XRD analysis, thescan rate of the X-ray generator 60 and detector 70 may be about 5°/min.

FIG. 3 is a conceptual view for illustrating an X ray intensity measuredby performing normal mode XRD analysis to a phase shift film, in a blankmask according to one embodiment. FIG. 4 is a conceptual view forillustrating an X ray intensity measured by performing normal mode XRDanalysis to a transparent substrate. An embodiment will be describedwith reference to the FIGS. 3 and 4.

When normal mode XRD analysis is performed on the upper surface of thephase shift film, 2θ of the maximum peak of the measured X-ray intensitymay be 15° to 30°. When normal mode XRD analysis is performed on thelower surface of the transparent substrate, 2θ of the maximum peak ofthe X-ray intensity measured may be 15° to 30°.

Hereinafter, when the XRD analysis is performed in the phase shift film,it means that the XRD analysis is performed on the upper surface of thephase shift film of the blank mask, and XRD analysis is performed in theside of the phase shift film. Similarly, when the XRD analysis isperformed on the transparent substrate, it means that the XRD analysisis performed on the lower surface of the transparent substrate, and itis also expressed that the XRD analysis is performed on the side of thetransparent substrate.

When the normal mode XRD analysis is performed on the phase shift film,2θ of the maximum peak of the measured X-ray intensity may be 20° to25°. When normal mode XRD analysis is performed on the transparentsubstrate, 2θ of the maximum peak of the measured X-ray intensity may be20° to 25°.

In addition, the absolute value of difference between the 2θ of themaximum peak of the X-ray intensity measured from the phase shift filmwhen the normal mode XRD analysis is performed on the phase shift filmand the 2θ of the maximum peak of the X-ray intensity measured from thetransparent substrate when the normal mode XRD analysis is performed onthe transparent substrate may be 5° or less. The absolute value may be3° or less. The absolute value may be 1° or less.

In the blank mask, the AI1 value of Equation 1 below may be 0.9 to 1.1.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Here, the XM1 is the maximum value of the X-ray intensity measured whenthe normal mode XRD analysis is performed on the front surface of thephase shift film, and the XQ1 is the maximum value of the X-rayintensity measured when the normal mode XRD analysis is performed on thelower surface of the transparent substrate.

The AI1 value may be 0.95 to 1.05. The AI1 value may be 0.97 to 1.03.The AI1 value may be 0.98 to 1.02. The AI1 value may be 0.99 to 1.01. Inthis case, it is possible to suppress a decrease in the resolution ofthe photomask due to a temperature change of long duration in theexposure process.

In the blank mask, the AI3 value expressed by Equation 3 below may be0.9 to 1.1.

$\begin{matrix}{{{AI}\; 3} = \frac{{AM}\; 1}{{AQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, the AM1 is the area of a region where 2θ is 15° to 30° in theX-ray intensity measured when XRD analysis is performed on the uppersurface of the phase shift film, and the AQ1 is the area of the regionwhere 2θ is 15° to 30° in the measured X-ray intensity XRD analysis onthe lower surface of the transparent substrate.

The AI3 value may be 0.95 to 1.05. The AI3 value may be 0.97 to 1.03.The AI3 value may be 0.98 to 1.02. The AI3 value may be 0.99 to 1.01. Insuch a case, the difference in crystal characteristics between thetransparent substrate and the phase shift film is reduced, and thusdeterioration of the patterned phase shift film due to temperaturechange can be suppressed.

In the blank mask, an AI4 value expressed by Equation 4 below may be 0.9to 1.1.

$\begin{matrix}{{{AI}\; 4} = \frac{{XM}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Here, the XM4 is the X-ray intensity where 2θ is 43° when the XRDanalysis is performed on the upper surface of the phase shift film and,and the XQ4 is the X-ray intensity where 2θ is 43° when the XRD analysisis performed on the lower surface of the transparent substrate.

The AI4 value may be 0.95 to 1.05. The AI4 value may be 0.97 to 1.03.The AI4 value may be 0.98 to 1.02. The AI4 value may be 0.99 to 1.01.

In such a case, the difference in thermal variation characteristicsbetween the transparent substrate and the phase shift film can beeffectively reduced.

FIG. 5 is a schematic view for illustrating fixed mode XRD analysis.Hereinafter, an embodiment will be described with reference to FIG. 5.

The XRD analysis may proceed as a fixed mode XRD analysis. In the fixedmode XRD analysis, X-rays are generated from the X-ray generator 60 andemitted to the sample 80, and the X-rays reflected from the sample 80are detected through the detector 70.

At this time, in the fixed mode XRD analysis, the X-ray generator 60emits X-rays to the sample 80 at a fixed incident angle (eg, 1°). Theincident angle is an angle between the direction of the X-rays emittedfrom the X-ray generator 60 and the horizontal plane of the sample 80.

The detector 70 is disposed opposite to the location where the X-raygenerator 60 is disposed based on the location where the X-rays of thesample 80 are incident. Also, the detector 70 detects X-rays having apredetermined emission angle θ among the X-rays reflected from thesample 80. The emission angle θ is the angle between the direction ofthe X-ray reflected from the sample 80 and the horizontal plane of thesample 80.

The detector 70 may be moved to detect X-rays emitted at variousemission angles θ. In the fixed mode XRD analysis, the position of theX-ray generator 60, the detector 70 and the site of the sample 80 to bemeasured are arranged in the same plane. Also, in the same plane, thedetector 70 may move. In addition, the detector 70 may be moved so thatthe distance from the position where the X-rays are reflected from thesample 80 is constant. That is, the detector 70 may be moved whiledrawing an arc.

In the fixed mode XRD analysis, the incident angle is about 1°, theX-ray source is a copper target (Cu target), the wavelength of the X-rayis about 1.542 nm, the voltage used to generate the X-ray is about 45kV, the current used to generate the X-rays is about 200 mA, themeasurement range of 2θ is about 10° to about 100°, and the measurementis performed every time it changes about 0.05° based on 2θ, and, thescan rate of the detector 2θ is about 5°/min

FIG. 6 is a conceptual view for illustrating an X ray intensity measuredby performing fixed mode XRD analysis to a phase shift film in a blankmask according to one embodiment. FIG. 7 is a conceptual view forillustrating an X ray intensity measured by performing fixed mode XRDanalysis to a transparent substrate in a blank mask according to oneembodiment. An embodiment will be described with reference to the FIGS.6 and 7.

When the fixed mode XRD analysis is performed, 2θ of the first peak,which is the maximum peak of the X-ray intensity measured from the uppersurface of the phase shift film, may be 15° to 25°. When the fixed modeXRD analysis is performed, 2θ of the second peak, which is the maximumpeak of the X-ray intensity measured from the lower surface of thetransparent substrate, may be 15° to 25°.

2θ of the first peak may be 17° to 23°, and 2θ of the second peak may be17° to 23°.

2θ of the first peak may be 19° to 22°, and 2θ at the second peak may be19° to 22°.

An absolute value of a difference between 2θ of the first peak and 2θ ofthe second peak may be 5° or less. The absolute value may be 3° or less.The absolute value may be 2° or less.

The blank mask may have an AI2 value of 0.9 to 1.1 expressed by Equation2 below.

$\begin{matrix}{{{AI}\; 2} = \frac{{XM}\; 2}{{XQ}\; 2}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Here, the XM2 is the intensity value of the first peak, and the XQ2 isthe intensity value of the second peak.

The AI2 value may be 0.95 to 1.05. The AI2 value may be 0.97 to 1.03.The AI2 value may be 0.98 to 1.02. In such a case, optical distortionthat may occur at the interface between the transparent substrate andthe phase shift film can be suppressed.

Crystal Characteristics of Light Shielding Film

The light shielding layer may comprise a relatively high content ofmetal elements compared to other films comprised in the blank mask. Forthis reason, the light shielding film may have a relatively largedimensional variation in the thickness direction according to thetemperature change compared to other films. When the light shieldinglayer is patterned to form a blind pattern together with the phase shiftfilm, the shape of the patterned light shielding film may be deformeddue to heat generated from a high-power light source for exposure. Thismay cause difficulties in developing a minute pattern on a semiconductorwafer precisely.

The example embodiment may provide a blank mask in which the shapedeformation of the light-shielding pattern film is suppressed even in anexposure process performed repeatedly and for a long time by controllingthe crystal characteristics of the light shielding film and thetransparent substrate measured by XRD.

FIG. 8 is a conceptual view for illustrating an X ray intensity measuredby performing normal mode XRD analysis to a light shielding film in ablank mask according to an embodiment. An embodiment will be describedwith reference to FIG. 8.

When normal mode XRD analysis is performed on the upper surface of thelight shielding film, 2θ of the maximum peak of the X-ray intensitymeasured may be 15° to 30°. When normal mode XRD analysis is performedon the lower surface of the transparent substrate, 2θ of the maximumpeak of the measured X-ray intensity measured is 15° to 30°.

The blank mask may have an AI5 value of 0.5 to 0.97 expressed byEquation 5 below.

$\begin{matrix}{{{AI}\; 5} = \frac{{XC}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Here, the XC1 is the intensity value of the maximum peak of X-rayintensity measured by normal mode XRD analysis on the upper surface ofthe light shielding film, and the XQ1 is the intensity value of themaximum peak of X-ray intensity measured by normal mode XRD analysis onthe lower surface of the transparent substrate.

The AI5 value may be 0.7 to 0.97. The AI5 value may be 0.5 to 0.95. TheAI5 value may be 0.7 to 0.95. The AI5 value may be 0.7 to 0.93. The AI5value may be 0.9 to 0.93. In such a case, it is possible to suppress theshape deformation of the blind pattern due to the exposure process witha light of short wavelength.

The blank mask may have an AI6 value of 1.05 to 1.4 expressed byEquation 6 below.

$\begin{matrix}{{{AI}\; 6} = \frac{{XC}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

Here, the XC4 is an X-ray intensity value at 2θ of 43° when the normalmode XRD analysis is performed on the upper surface of the lightshielding film, and the XQ4 is an X-ray intensity value at 2θ of 43°when the normal mode XRD analysis is performed on the lower surface ofthe transparent substrate.

The AI6 value may be 1.06 to 1.4. The AI6 value may be 1.07 to 1.4. TheAI6 value may be 1.08 to 1.4. In such a case, it is possible to suppressthe dimensional variation in the thickness direction of the lightshielding film according to the temperature change.

Layer Structure of Phase Shift Film

FIG. 9 is a sectional view for illustrating a blank mask according toanother embodiment. An embodiment will be described with reference toFIG. 9.

The phase shift film 20 may comprise a phase difference adjustment layer21 and a protective layer 22 disposed on the phase difference adjustmentlayer 21.

The phase shift film 20, the phase difference adjustment layer 21, andthe protective layer 22 may comprise a transition metal, silicon,oxygen, and nitrogen.

The phase difference adjustment layer 21 is a layer in which thetransition metal, silicon, oxygen, and nitrogen are uniformly comprisedwithin the range of 5 atom % in the depth direction in the phase shiftfilm 20. The phase difference adjustment layer 21 may substantiallyadjust the phase difference and transmittance of light transmitting thephase shift film 20.

In detail, the phase difference adjustment layer 21 has a characteristicof shifting the phase of the exposure light incident from the back sideof the transparent substrate 10. Due to these characteristics, the phaseshift film 20 effectively cancels the diffracted light generated at theedge of the transmissive portion in the photomask, so that theresolution of the photomask is further improved during the lithographyprocess.

In addition, the phase difference adjustment layer 21 attenuates theexposure light incident from the back side of the transparent substrate10. Through this, the phase shift film 20 may block the transmission ofthe exposure light while canceling the diffracted light generated at theedge of the transmissive portion.

The protective layer 22 is formed on the surface of the phase shiftfilm, and is a layer having a distribution in which the oxygen contentis continuously decreased in the depth direction from the surface andthe nitrogen content is continuously increased. The protective layer 22may improve the durability of the phase shift film 20 by suppressingdamage to the phase shift film 20 or the patterned phase shift film inthe etching process or cleaning process of the photomask. In addition,the protective layer 22 may suppress oxidation of the phase differenceadjustment layer 21 due to exposure light in the exposure process.

Optical Properties of Phase Shift Film Measured with Ellipsometer

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is 3.0eV, the photon energy of incident light at the point where the Del_1value is 0 according to Equation 7 below may be 1.8 eV to 2.14 eV.

$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta\;{PE}}\rightarrow 0}\left( \frac{\Delta\;{DPS}}{\Delta\;{PE}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

In the Equation 7, the DPS value is, when the light shielding film isremoved from the blank mask and the surface of the phase shift film ismeasured with a spectroscopic ellipsometer by applying an incident angleof 64.5°, the phase difference between the P wave and the S wave of thereflected light if the phase difference between the P wave and the Swave of the reflected light is 180° or less, or a value obtained bysubtracting the phase difference between the P wave and the S wave from360° when the phase difference between the P wave and the S wave is morethan 180°.

The PE value is the photon energy of the incident light within the rangeof the PE₁ value to the PE₂ value.

The resolution of the photomask can be improved by precisely adjustingthe optical properties of the phase shift film 20.

In detail, the phase difference and transmittance with respect to theexposure light of the phase shift film 20 may be simultaneouslyadjusted. The phase difference and transmittance of the phase shift film20 may be controlled by adjusting ingredients, thickness, and the likeof the phase shift film. The thickness, transmittance and phase shift ofthe phase shift film 20 have characteristics that are related to eachother. However, the phase difference and the transmittance have atrade-off relationship in which it is difficult to simultaneously havethe intended values.

In the embodiment, by controlling the phase difference distribution ofthe P wave and S wave of the phase shift film measured with anellipsometer, a phase shift film 20 which is further thinned andsimultaneously having phase difference and transmittance for light witha wavelength of 200 nm or less controlled within the ranges preset inthe embodiment.

FIG. 10 is a conceptual view for showing a principle for measuring aphase difference between P wave and S wave of reflected light of a phaseshift film with a spectroscopic ellipsometer. An embodiment will bedescribed with reference to FIG. 10.

The phase difference (Δ) value between the P wave (P′) and the S wave(S′) of the reflected light (Lr) may vary depending on the photon energyof the incident light (Li) of the spectroscopic ellipsometer at a fixedangle of incidence (θ). The Del_1 value is calculated by measuring thephase difference (Δ) between the P wave (P′) and the S wave (S′) of thereflected light (Lr) with respect to the photon energy of the incidentlight (Li) of the phase shift film 20.

The Del_1 value distribution can be adjusted by controlling variousfactors such as elements constituting the phase shift film 20, theconditions of a sputtering process, the thickness of a phase shift film,and an incident angle set by a spectroscopic ellipsometer. Inparticular, the distribution of the Del_1 value of the phase shift film20 may be controlled by adjusting the strength of a magnetic fieldapplied to form the phase shift film 20.

The Del_1 value is measured with a spectroscopic ellipsometer. Forexample, the phase difference (Δ) between the P wave (P′) and the S wave(S′) of the reflected light (Lr) of the phase shift film may be measuredthrough the MG-PRO model available from NANO-VIEW.

When the Del_1 value distribution of the phase shift film 20 ismeasured, the measurement is performed after the light shielding layerplaced on the phase shift film 20 is removed. When another film isplaced between the phase shift film 20 and the light shielding film, theother film is also removed. As methods for removing the light shieldingfilm and the other films, an etching method and the like may be applied.However, the present application is not limited thereto. Since it istechnically difficult to remove the other film placed on the phase shiftfilm without damage to the phase shift film 20, damage of 1 nm or lessin the thickness direction to the phase shift film during the etchingprocess is allowed.

In the blank mask, when the PE_(I) value is 1.5 eV and the PE₂ value is3.0 eV, the photon energy of incident light at the point where the Del_1value is 0 may be 1.8 eV to 2.14 eV. The photon energy of incident lightmay be 1.85 eV to 2.1 eV. The photon energy of incident light may be 1.9eV to 2.05 eV. In this case, the phase shift film 20 may have a desiredtransmittance and a phase difference with respect to exposure lighthaving a short wavelength, and may have a smaller thickness.

In the blank mask, when the PE₁ value is 3 eV and the PE₂ value is 5 eV,the photon energy of incident light at the point where the Del_1 valueis 0 may be 3.8 to 4.64 eV.

When the incident light (Li) having high photon energy of incident lightis irradiated to the measuring target, the incident light (Li) isreflected at a shallow depth from the surface or the surface of thephase shift film 20 due to the short wavelength of the incident light(Li). When the phase difference of reflected light formed by irradiatingincident light (Li) with high photon energy to the surface of the phaseshift film 20 is analyzed, the optical properties of the upper part ofthe phase shift film 20, especially the optical properties of theprotective layer 22 can be ascertained.

The protective layer 22 is placed on the phase difference adjustmentlayer 21 to protect the phase difference adjustment layer 21 fromexposure light and a cleaning solution. As the thickness of theprotective layer 22 increases and the protective layer 22 has a densestructure, the protective layer 22 can more stably protect the phasedifference adjustment layer 21. However, when the protective layer 22 isformed in consideration of only the stable protection of the phasedifference adjustment layer 21, the optical property variation of theentire phase shift film 20 may occur quite significantly due to theeffect of the formation of the protective layer 22. In such a case, thephase shift film 20 may have a characteristic that deviates from theoriginally designed optical properties. The embodiment can provide aphase shift film 20 in which a phase difference adjustment layer 21 isstably protected and the optical properties is not significantly variedcompared to before the formation of the protective layer 22, bycontrolling the P wave and S wave distribution characteristics of thephase shift film 20.

When the PE₁ value is 3 eV and the PE₂ value is 5 eV, the photon energydistribution of incident light at the point where the Del_1 value is 0can be adjusted by controlling factors such as the composition ofatmospheric gas of sputtering, the annealing temperature, and thetemperature increase rate during the annealing process of the phasedifference adjustment layer 21. In particular, it is possible to controlthe Del_1 value by controlling the heat treatment temperature and timeduring the annealing process after UV light treatment on the surface ofthe phase difference adjustment layer 21.

In the blank mask 100, when the PE₁ value is 3 eV and the PE₂ value is 5eV, the photon energy of incident light at the point where the Del_1value is 0 may be 3.8 eV or more. The photon energy of incident lightmay be 4 eV or more. The photon energy of incident light may be 4.2 eVor more. The photon energy of incident light may be 4.3 eV or more. Thephoton energy of incident light may be 4.64 eV or less. The photonenergy of incident light may be 4.62 eV or less. The photon energy ofincident light may be 4.6 eV or less. In such a case, while theprotective layer 22 sufficiently protects the phase differenceadjustment layer 21, the optical property variation of the phase shiftfilm 20 due to the formation of the protective layer 22 may becontrolled within a predetermined range.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value isthe minimum value within photon energy values of the incident light atthe point where the Del_1 value is 0, the average value of Del_1 may be78°/eV to 98°/eV.

When the photon energy of the incident light has a value within therange of 1.5 eV or more and less than or equal to the minimum value ofthe photon energy of the incident light at the point where the Del_1value is 0, the incident light has a relatively long wavelength value.Since this incident light is reflected after being transmittedrelatively deeply into the phase shift film, the average value of Del_1measured by setting the photon energy of incident light in the samerange as above shows the optical properties of the phase differenceadjustment layer 21 in the phase shift film 20.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value isthe minimum value within photon energy values of the incident light atthe point where the Del_1 value is 0, the average value of the Del_1value may be 78 to 98°/eV. The average value may be 80 to 95°/eV. Theaverage value may be 82 to 93°/eV. In such a case, the phase differenceadjustment layer 21 may help the phase shift film 20 to have a desiredphase difference and transmittance for light of a short wavelength whilehaving a relatively low thickness.

In the blank mask 100, when the PE₁ value is the minimum value withinthe photon energy values of the incident light at the point where theDel_1 value is 0, and the PE₂ value is the maximum value within thephoton energy values of the incident light at the point where the Del_1value is 0, the average value of Del_1 may be −65 to −55°/eV.

When the value of the photon energy of the incident light is greaterthan the minimum value within the photon energy values of the incidentlight at the point where the Del_1 value is 0, and the PE₂ value has avalue within the range of less than or equal to the maximum value of thephoton energy of the incident light at the point where the Del_1 valueis 0, the average value of the Del_1 value measured by applying such acondition shows the optical properties of a portion located near theinterface between the phase difference adjustment layer 21 and theprotective layer 22.

In the blank mask 100, the PE₁ value is the minimum value within photonenergy values of the incident light at the point where the Del_1 valueis 0, and the PE₂ value is the maximum value within the photon energyvalues of the incident light at the point where the Del_1 value is 0,the average value of Del_1 may be −65 to −55°/eV. The average value maybe −62 to −56°/eV. The average value may be −59 to −57°/eV. In such acase, it is possible to suppress the interface formed between the phasedifference adjustment layer 21 and the protective film 22 from greatlyaffecting the optical properties of the entire phase shift film.

In the blank mask 100, the PE₁ value is the maximum value within photonenergy values of the incident light at the point where the Del_1 valueis 0, and when the PE₂ value is 5.0 eV, the average value of Del_1 maybe 60 to 120°/eV.

The average value of Del_1 measured by setting the PE₁ value to be themaximum value within photon energy values of incident light at the pointwhere the Del_1 value is 0 and the PE₂ value to be 5.0 eV shows theoptical properties of the protective layer 22.

In the blank mask 100, when the PE₁ value is the maximum value withinphoton energy values of the incident light at the point where the Del_1value is 0, and when the PE₂ value is 5.0 eV, the average value of theDel_1 value may be 60°/eV to 120°/eV. The average value may be 70 to110°/eV. The average value may be 80 to 105°/eV. In such a case, thephase shift film 20 may have stable durability while reducing theinfluence of the protective layer 22 on the optical properties of theentire phase shift film 20.

In the blank mask 100, when PE₁ value is 1.5 eV and PE₂ value is 3.0 eV,the absolute value of a difference value between a photon energy valueof incident light which is measured after the formation of theprotective layer 22 at the point where the Del_1 value is 0 and thephoton energy value of the incident light measured before the formationof the protective layer 22 at the point where the Del_1 value is 0 maybe 0.001 to 0.2 eV.

In the process of forming the protective layer 22 on the phasedifference adjustment layer 21, a change in optical properties of thephase difference adjustment layer 21 itself may occur. In detail, whenannealing is applied to the phase difference adjustment layer undercontrolled atmospheric pressure and temperature conditions, residualstress in the phase difference adjustment layer and the composition ofthe surface of the phase difference adjustment layer may be changed.Such variations may cause variations in the optical properties of thephase difference adjustment layer itself. This may cause the phase shiftfilm to have characteristics deviating from the optical propertiesdesired in the embodiment. The embodiment can provide a blank maskcapable of exhibiting higher resolution by controlling the differencevalue of the optical properties of the phase difference adjustment layeritself before and after forming the protective layer.

In the blank mask 100, when PE₁ value is 1.5 eV and PE₂ value is 3.0 eV,the absolute value of a difference value between a photon energy valueof incident light which is measured after the formation of theprotective layer 22 at the point where the Del_1 value is 0 and thephoton energy value of the incident light measured before the formationof the protective layer 22 at the point where the Del_1 value is 0 maybe 0.001 to 0.2 eV. The absolute value may be 0.005 to 0.1 eV. Theabsolute value may be 0.01 to 0.008 eV. In such a case, a blank mask 100may suppress optical variations of the phase difference adjustment layer21 itself caused from the formation of the protective layer 22.

In the blank mask 100, when PE₁ value is 3.0 eV and PE₂ value is 5.0 eV,the absolute value of a difference value between a photon energy valueof incident light which is measured after the formation of theprotective layer 22 at the point where the Del_1 value is 0 and thephoton energy value of the incident light measured before the formationof the protective layer 22 at the point where the Del_1 value is 0 maybe 0.05 to 0.3 eV. The absolute value may be 0.06 to 0.25 eV. Theabsolute value may be 0.1 to 0.23 eV. In such a case, the blank mask 100may reduce the influence of the optical properties of the protectivelayer 22 itself on the optical properties of the entire phase shift film20.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value is5.0 eV, the maximum value of Del_1 may be 105°/eV to 300°/eV.

In the embodiment, by adjusting the maximum value of Del_1 when the PE₁value of the blank mask 100 is 1.5 eV and the PE₂ value is 5.0 eV, thephase shift film 20 can have stable durability while adjusting theoptical property variation of the entire phase shift film 20 due to theformation of the protective layer 22 within a predetermined range.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value is5.0 eV, the maximum value of Del_1 may be 105 to 300°/eV. The maximumvalue is 120 to 200 eV. The maximum value may be 140 to 160 eV. In sucha case, the phase shift film 20 may have excellent light resistance,chemical resistance, and the like, while reducing the variation of theoptical properties of the entire phase shift film 20 due to theformation of the protective layer 22.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value is5.0 eV, the photon energy of incident light at the point where the Del_1is the maximum value may be 4.5 eV or more.

When the PE₁ value is 1.5 eV and the PE₂ value is 5.0 eV, the maximumvalue of Del_1 is influenced by the optical properties of the protectivelayer 22 and the like. The embodiment can reduce the influence of theprotective layer 22 on the optical properties of the entire phase shiftfilm 20 while maintaining stable durability by adjusting the photonenergy of incident light at the point having the maximum value of Del_1.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value is5.0 eV, the photon energy of incident light at the maximum value ofDel_1 may be 4.5 eV or more. The photon energy of incident light at thepoint where the Del_1 is the maximum value may be 4.55 eV or more. Aphoton energy of incident light at the point having the maximum value ofDel_1 may be 5 eV or less. The photon energy of incident light at thepoint having the maximum value of Del_1 may be 4.8 eV or less. In such acase, the phase shift film 20 can exhibit desired optical propertieswith respect to light with a short wavelength, and at the same time cansuppress optical property variations due to exposure and cleaningprocesses.

In the blank mask 100, when the PE₁ value is 1.5 eV and the PE₂ value is5.0 eV, a value obtained by subtracting the minimum value of Del_1 fromthe maximum value of Del_1 may be 60 to 260 eV.

The inventors of the present disclosure ascertained the follows throughexperiments; when the PE₁ value is 1.5 eV and the PE₂ value is 5.0 eV,the maximum value of Del_1 shows the optical properties of theprotective layer 22, and the minimum value of the Del_1 shows theoptical properties of the upper portion of the phase differenceadjustment layer 21.

When the PE₁ value is 1.5 eV and the PE₂ value is 5.0 eV, the maximumvalue of Del_1 and the minimum value of Del_1 may vary before and afterthe formation of the protective layer. When the value obtained bysubtracting the minimum value of Del_1 from the maximum value of Del_1is controlled within a predetermined range, optical property variationof the entire phase shift film 20 before and after formation of theprotective layer 22 may occur within an allowable range.

In the blank mask, when the PE₁ value is 1.5 eV and the PE₂ value is 5.0eV, a value obtained by subtracting the minimum value of Del_1 from themaximum value of Del_1 may be 60 to 260 eV. A value obtained bysubtracting the minimum value of Del_1 from the maximum value of Del_1may be 80 to 240 eV. A value obtained by subtracting the minimum valueof Del_1 from the maximum value of Del_1 may be 90 to 230 eV. In such acase, the optical property variation of the entire phase shift filmbefore and after formation of the protective layer may be controlledwithin a predetermined range.

Composition of Phase Shift Film

The phase shift film 20 may comprise a transition metal, silicon,oxygen, and nitrogen. The transition metal may be one or more elementsselected from molybdenum (Mo), tantalum (Ta), zirconium (Zr), and thelike, but is not limited thereto. For example, the transition metal maybe molybdenum.

The phase shift film 20 may comprise a transition metal of 1 to 10 atom%. The phase shift film 20 may comprise a transition metal of 2 to 7atom %. The phase shift film 20 may comprise silicon in an amount of 15to 60 atom %. The phase shift film 20 may comprise silicon in an amountof 25 to 50 atom %. The phase shift film 20 may comprise nitrogen in anamount of 30 to 60 atom %. The phase shift film 20 may comprise nitrogenin an amount of 35 to 55 atom %. The phase shift film 20 may compriseoxygen in an amount of 5 to 35 atom %. The phase shift film 20 maycomprise oxygen in an amount of 10 to 25 atom %. In such a case, thephase shift film 20 may have optical properties suitable for alithography process using exposure light having a short wavelength,specifically, light having a wavelength of 200 nm or less.

The phase shift film 20 may additionally comprise other elements inaddition to the above-mentioned elements. For example, the phase shiftfilm 20 may comprise argon (Ar), helium (He), or the like.

The phase shift film 20 may have different content for each element inthe thickness direction.

The content distribution for each element formed in the depth directionof the phase difference adjustment layer 21 and the protective layer 22may be ascertained by measuring a depth profile of the phase shift film20. The depth profile of the phase shift film 20 may be measured using,for example, a K-alpha model available from THERMO SCIENTIFIC.

The phase difference adjustment layer 21 and the protective layer 22 mayhave different contents of each element, such as a transition metal,silicon, oxygen, and nitrogen.

The phase difference adjustment layer 21 may comprise a transition metalof 3 to 10 atom %. The phase difference adjustment layer 21 may comprisea transition metal of 4 to 8 atom %. The phase difference adjustmentlayer 21 may comprise silicon in an amount of 20 to 50 atom %. The phasedifference adjustment layer 21 may comprise silicon in an amount of 30to 40 atom %. The phase difference adjustment layer 21 may compriseoxygen in an amount of 2 to 10 atom %. The phase difference adjustmentlayer 21 may comprise oxygen in an amount of 3 to 8 atom %. The phasedifference adjustment layer 21 may comprise nitrogen in an amount of 40to 60 atom %. The phase difference adjustment layer 21 may comprisenitrogen in an amount of 45 to 55 atom %. In such a case, when exposurelight having a short wavelength, specifically light having a wavelengthof 200 nm or less, is applied as the exposure light, the blank mask mayhave excellent pattern resolution.

As the protective layer 22 comprises more oxygen, it is possible tostably protect the phase difference adjustment layer 21 from exposurelight and a cleaning solution. However, such a protective layer 22 mayhave a greater effect on the optical property variation of the entirephase shift film 20 that occurs before and after the formation of theprotective layer 22. Accordingly, by controlling the contentdistribution of oxygen and nitrogen in the protective layer 22, thephase shift film 20 may have sufficient light resistance and chemicalresistance while having desired optical properties in the embodiment.

The protective layer 22 may comprise nitrogen in an amount of 20 to 40atom %. The protective layer 22 may comprise nitrogen in an amount of 25to 35 atom %. The protective layer 22 may comprise oxygen in an amountof 10 to 50 atom %. The protective layer 22 may comprise oxygen in anamount of 20 to 40 atom %. The protective layer 22 may comprise siliconin an amount of 10 to 50 atom %. The protective layer 22 may comprisesilicon in an amount of 20 to 40 atom %. The protective layer 22 maycomprise a transition metal in an amount of 0.5 to 5 atom %. Theprotective layer 22 may comprise a transition metal in an amount of 1 to3 atom %. In such a case, the protective layer 22 can sufficientlysuppress the deterioration of the phase difference adjustment layer 21.

The protective layer 22 may comprise a region in the thickness directionin which the nitrogen content (atom %) to the oxygen content (atom %) is1 or more. The region may have a thickness of 40 to 60% of a totalthickness of the protective layer 22. The region may have a thickness of45 to 55% of a total thickness of the protective layer 22. In such acase, it is possible to effectively suppress variations in the opticalproperties of the phase shift film 20 due to the formation of theprotective layer 22.

The protective layer 22 may comprise a region in which the ratio of thenitrogen content (atom %) to the oxygen content (atom %) in thethickness direction is 0.4 to 2, and the region may have a thickness of30 to 80% compared to a total thickness of the protective layer 22. Theregion may have a thickness of 40 to 60% compared to a total thicknessof the protective layer 22. In such a case, it is possible to provide ablank mask capable of manufacturing a photomask having excellentresolution while having sufficient long-term durability.

The thickness of the region in which the ratio of the nitrogen content(atom %) to the oxygen content (atom %) in the thickness direction isadjusted may be ascertained by measuring the depth profile. However, itis assumed that the etching rate for each depth of the protective layer22 is constant in the depth profile when the thickness of the region ismeasured.

Optical Properties and Thickness of Each Layer of Phase Shift Film

The phase shift film 20 may have a phase difference of 160 to 200° withrespect to light having a wavelength of 200 nm or less. The phase shiftfilm 20 may have a phase difference of 160 to 200° with respect to ArFlight. The phase shift film 20 may have a phase difference of 170 to190° with respect to light having a wavelength of 200 nm or less. Thephase shift film 20 may have a phase difference of 170 to 190° withrespect to ArF light. The phase shift film 20 may have a transmittanceof 3 to 10% for light having a wavelength of 200 nm or less. The phaseshift film 20 may have a transmittance of 3 to 10% for ArF light. Thephase shift film 20 may have a transmittance of 4 to 8% for light havinga wavelength of 200 nm or less. The phase shift film 20 may have atransmittance of 4 to 8% for ArF light. In such a case, the photomaskcomprising the phase shift film 20 may form a more precise minutepattern on the wafer in an exposure process to which exposure light of ashort wavelength is applied.

The protective layer 22 may have a refractive index of 1.3 to 2 forlight having a wavelength of 200 nm or less. The protective layer 22 mayhave a refractive index of 1.3 to 2 for ArF light. A refractive index ofthe protective layer 22 with respect to light having a wavelength of 200nm or less may be 1.4 to 1.8. A refractive index of the protective layer22 with respect to ArF light may be 1.4 to 1.8. An extinctioncoefficient for light having a wavelength of 200 nm or less of theprotective layer 22 may be 0.2 to 0.4. An extinction coefficient for ArFlight of the protective layer 22 may be 0.2 to 0.4. The protective layer22 may have an extinction coefficient of 0.25 to 0.35 for light having awavelength of 200 nm or less. An extinction coefficient of theprotective layer 22 with respect to ArF light may be 0.25 to 0.35. Insuch a case, the optical property variation of the phase shift film 20due to the formation of the protective layer 22 may be minimized.

The phase difference adjustment layer 21 may have a refractive index of2 to 4 for light having a wavelength of 200 nm or less. The phasedifference adjustment layer 21 may have a refractive index of 2 to 4 forArF light. The refractive index of the phase difference adjustment layer21 with respect to light having a wavelength of 200 nm or less may be2.5 to 3.5. The refractive index of the phase difference adjustmentlayer 21 with respect to ArF light may be 2.5 to 3.5. An extinctioncoefficient for light having a wavelength of 200 nm or less of the phasedifference adjustment layer 21 may be 0.3 to 0.7. The extinctioncoefficient for ArF light of the phase difference adjustment layer 21may be 0.3 to 0.7. An extinction coefficient for light having awavelength of 200 nm or less of the phase difference adjustment layer 21may be 0.4 to 0.6. The extinction coefficient for ArF light of the phasedifference adjustment layer 21 may be 0.4 to 0.6. In such a case, theresolution of the photomask comprising the phase shift film 20 may befurther improved.

The optical properties of the phase shift film 20, the protective layer22, and the phase difference adjustment layer 21 may be measured using aspectroscopic ellipsometer. For example, the optical properties may bemeasured through MG-PRO equipment of NANO-VIEW.

A ratio of the thickness of the protective layer 22 to a total thicknessof the phase shift film 20 may be 0.04 to 0.09. The thickness ratio maybe 0.05 to 0.08. In such a case, the protective layer 22 may stablyprotect the phase difference adjustment layer 21.

The thickness of the protective layer 22 may be 25 Å or more and 80 Å orless. The thickness of the protective layer 22 may be 35 Å or more and45 Å or less. In such a case, it is possible to provide the phase shiftfilm 20 that effectively reduces the degree of change in opticalproperties on the entire phase shift film and exhibits stable opticalproperties even in an exposure process and a cleaning processlong-duration.

The phase shift film 20 and the thickness of each layer constituting thephase shift film 20 may be measured through a TEM image of a crosssection of the phase shift film 20.

Layer Structure, Composition and Optical Properties of Light ShieldingFilm

The light shielding film 30 may be disposed on the phase shift film 20.The light shielding layer 30 may be used as an etching mask of the phaseshift film 20 when the phase shift film 20 is etched according to apreviously designed pattern shape. In addition, the light shielding film30 may block transmission of the exposure light incident from the rearside of the transparent substrate 10.

The light shielding film 30 may have a single-layer structure. The lightshielding film 30 may have a multi-layer structure of two or more films.In the light shielding film 30 sputtering process, multi-layer lightshielding films 30 may be formed by applying different atmospheric gascompositions and flow rates for each layer in the light shielding film.In the light shielding film 30 sputtering process, multi-layer lightshielding films 30 may be formed by applying different sputteringtargets for each layer in the light shielding film.

The light shielding layer 30 may comprise chromium, oxygen, nitrogen,and carbon. The content of each element in the light shielding film 30may be different in the thickness direction of the light shielding layer30. In a case of a light shielding film with plural layers, therespective layers in the light shielding film 30 may have differentcompositions each other.

The light shielding layer 30 may comprise chromium in an amount of 30 to70 atom %. The light shielding layer 30 may comprise chromium in anamount of 47 to 57 atom %. The light shielding film 30 may comprisecarbon in an amount of 5 to 30 atom %. The light shielding layer 30 maycomprise carbon in an amount of 7 to 25 atom %. The light shieldinglayer 30 may comprise nitrogen in an amount of 3 to 30 atom %. The lightshielding layer 30 may comprise nitrogen in an amount of 5 to 25 atom %.The light shielding layer 30 may comprise oxygen in an amount of 20 to55 atom %. The light shielding layer 30 may comprise oxygen in an amountof 25 to 40 atom %. In such a case, the light shielding film 30 may havesufficient extinction characteristics.

The multilayer film (not shown) comprises a phase shift film 20 and alight shielding film 30. The multilayer film may form a blind pattern onthe transparent substrate 10 to suppress transmission of the exposurelight.

The optical density of the multilayer film with respect to light havinga wavelength of 200 nm or less may be 3 or more. The optical density ofthe multilayer film for ArF light may be 3 or more. The optical densityof the multilayer film for light having a wavelength of 200 nm or lessmay be 3.5 or more. The optical density of the multilayer film for ArFlight may be 3.5 or more. In such a case, the multilayer film may haveexcellent light blocking properties.

Manufacturing Method of Phase Shift Film

The phase difference adjustment layer among the phase shift films of theembodiment may be manufactured by sputtering on a transparent substrate.

The sputtering process may use DC power or RF power.

A target and a sputtering gas may be selected in consideration of thecomposition of the phase shift film to be formed.

In the case of a sputtering target, one target comprising a transitionmetal and silicon may be applied, and a target comprising a transitionmetal and a target comprising silicon may be applied simultaneously.When a target is applied as a sputtering target, the transition metalcontent relative to the sum of the transition metal and silicon contentsof the target may be 30% or less. The transition metal content relativeto the sum of the transition metal and silicon content of the target maybe 20% or less. The transition metal content relative to the sum of thetransition metal and silicon content of the target may be 10% or less.The transition metal content relative to the sum of the transition metaland silicon content of the target may be 2% or more. In such a case, thephase shift film formed by sputtering applied to the target may havedesired optical properties.

In a case of the sputtering gas, CH₄ as a gas comprising carbon, O₂ as agas comprising oxygen, N₂ as a gas comprising nitrogen, etc., may beintroduced. However, the present disclosure is not limited thereto. Aninert gas may be added to the sputter gas. Examples of the inert gascomprise Ar, He, and the like. However, the present application is notlimited thereto. Depending on the type and content of the inert gas, thecrystal characteristics of the phase shift film formed by sputtering maybe adjusted. The sputtering gas may be individually introduced into thechamber for each gas. The sputtering gas may be introduced into thechamber by mixing respective gases.

A magnet may be disposed at the chamber so that the phase shift film hasmore uniformized crystal characteristics in the in-plane direction. Indetail, by disposing the magnet on the back side of the sputteringtarget and rotating the magnet at a predetermined speed, plasma can bemaintained at an even distribution on the front surface of the target.The magnet can be rotated at a speed of 50 to 200 rpm.

The rotation speed of the magnet may be fixed at a constant speed duringsputtering. The rotation speed of the magnet can be varied duringsputtering. The rotation speed of the magnet may be increased from theinitial rotation speed with uniform acceleration during sputtering.

The rotation speed of the magnet may be increased by 5 to 20 rpm perminute from the initial rotation speed during sputtering. The rotationspeed of the magnet may be increased by 7 to 15 rpm per minute from theinitial rotation speed during sputtering. In such a case, film qualitycharacteristics of the phase shift film in the thickness direction canbe more easily controlled.

When the magnetic field of the magnet is adjusted, the density of plasmaformed in the chamber is adjusted, thereby controlling the crystalcharacteristics of the phase shift film to be formed. The magnetic fieldof the magnet applied during sputtering may be 25 to 60 mT. The magneticfield may be 30 to 50 mT. In such a case, the phase shift film 20 to beformed may have crystal characteristics more similar to those of thetransparent substrate.

In the sputtering process, the T/S distance, which is the distancebetween the target and the substrate, and the angle between a surface ofthe substrate and the front surface of the target may be adjusted. TheT/S distance may be 240 to 260 mm The angle between the surface of thesubstrate and the front surface of the target may be 20 to 30 degrees.In such a case, the formation rate of the phase shift film is stablycontrolled, and it is possible to suppress an excessive increase in theinternal stress of the phase shift film.

In the sputtering process, the rotation speed of the substrate havingthe target surface for the phase shift film formation can be adjusted.The rotation speed of the substrate may be 2 to 20 RPM. The rotationspeed of the substrate may be 5 to 15 RPM. When the rotation speed ofthe substrate is adjusted within such a range, the formed phase shiftfilm may have stable durability while further improving the evenness ofoptical properties in the in-plane direction.

In addition, it is possible to adjust the intensity of power applied tothe sputtering target when the phase difference adjustment layer isformed. By supplying power to the sputtering target, a discharge regionincluding a plasma atmosphere in the chamber may be formed. The crystalcharacteristics of the phase shift film to be formed may be adjusted bycontrolling the electric power and simultaneously controlling themagnetic field and rotation speed of the magnet. The intensity ofelectric power applied to the sputtering target may be 1 to 3 kW. Theintensity of the electric power may be 1.5 to 2.5 kW. The intensity ofthe electric power may be 1.8 to 2.2 kW. In such a case, the thermalvariation in the thickness direction depending on the temperature of thephase shift film may be controlled within a predetermined range.

A spectroscopic ellipsometer may be installed in the sputteringequipment. Through this, it is possible to control the formation timewhile monitoring the optical properties of the phase differenceadjustment layer 21 to be formed. In detail, after setting the angleformed by the incident light with the surface of the phase differenceadjustment layer to be formed, it is possible to monitor the Del_1 valueof the phase difference adjustment layer 21 formed in real time duringthe film formation process. By performing the film forming process untilthe Del_1 value falls within the range preset in the embodiment, thephase shift film may have desired optical properties.

By measuring the phase difference between the P wave and S wave of thereflected light while changing the photon energy of the incident lightof the spectroscopic ellipsometer, the optical properties of each layerof the phase shift film can be measured. In detail, when the photonenergy of the incident light is set to be relatively low, the incidentlight forms a long wavelength, so that the optical properties of thelower layer of the phase shift film to be measured can be measured. Whenthe photon energy of the incident light is set to be relatively high,the incident light forms a short wavelength, so that the opticalproperties of the upper layer of the phase shift film to be measured canbe measured.

UV light may be irradiated to the surface of the phase differenceadjustment layer immediately after the sputtering process is completed.In the sputtering process, Si of the SiO₂ matrix constituting thetransparent substrate may be substituted with a transition metal, and Oof the SiO₂ matrix may be substituted with N. If the sputtering processis continued, it is out of the Solubility Limit of transition metal, andthe transition metal may be disposed in an interstitial site rather thanbeing substituted with Si in the SiO₂ matrix. In such a case, thetransition metal may form a mixture with elements such as Si, O, and N.The mixture may be in a homogeneous state or may be in an inhomogeneousstate.

When a non-uniform mixture is formed on the surface of the phasedifference adjustment layer, a haze defect may be formed on the surfaceof the phase difference adjustment layer by exposure light having ashort wavelength in the exposure process. When the cleaning process isperformed using sulfuric acid as a cleaning solution to remove the haze,sulfur ions may remain on the surface of the phase difference adjustmentlayer after the cleaning process. Residual sulfur ions may continuouslyreceive strong energy from exposure light in the wafer exposure process.Sulfur ions with high energy may react with the inhomogeneous mixture togenerate growth defects on the surface of the phase differenceadjustment layer. The embodiment can further improve the lightresistance and chemical resistance of the phase difference adjustmentlayer by irradiating UV light of a controlled wavelength to the surfaceof the phase difference adjustment layer to uniformize the transitionmetal and N content in the mixture of the surface of the phasedifference adjustment layer in the in-plane direction.

By using a light source having a power of 2 to 10 mW/cm², a light with awavelength of 200 nm or less is irradiated to the surface of the phasedifference adjustment layer for 5 to 20 minutes, and thereby the surfaceof the phase difference adjustment layer may be treated.

The phase difference adjustment layer 21 may be heat-treated togetherwith or separately from the UV light irradiation process. The heattreatment may be applied by utilizing the heat generated by UVirradiation or may be performed as separated processes.

The phase difference adjustment layer 21 formed through the sputteringprocess may have an internal stress. The internal stress may be acompressive stress or a tensile stress depending on the conditions ofsputtering. The internal stress of the phase difference adjustment layermay cause warpage of the substrate, and as a result, the resolution ofthe photomask to which the phase difference adjustment layer is appliedmay be reduced. In the embodiment, the warpage of the substrate may bereduced by applying a heat treatment to the phase difference adjustmentlayer.

The protective layer may be formed through a heat treatment processafter sputtering process of the phase difference. During the heattreatment process, an atmospheric gas in the chamber may be introducedto form a protective layer on the surface of the phase differenceadjustment layer 21. A protective layer may be formed by reacting thesurface of the phase difference adjustment layer with atmospheric gas inthe heat treatment process. However, the manufacturing method of theprotective layer is not limited thereto.

The heat treatment process may comprise a temperature increasingoperation, a temperature maintaining operation, a cooling operation, anda protective layer forming operation. The heat treatment process may beperformed by disposing a blank mask having a phase difference adjustmentlayer formed on the surface thereof in a chamber and then heating itthrough a lamp.

In the temperature increasing operation, the atmosphere temperature inthe heat treatment chamber may be raised to a set temperature of 150 to500° C.

In the temperature maintaining operation, the atmosphere temperature inthe chamber may be maintained at the set temperature, and the pressurein the chamber may be adjusted to be 0.1 to 2.0 Pa. The temperaturemaintaining operation may be carried out for 5 to 60 minutes.

In the cooling operation, the temperature in the chamber may be loweredfrom a set temperature to room temperature.

The protective layer forming operation is an operation of forming aprotective layer on the surface of the phase shift film by introducingan atmospheric gas comprising a reactive gas into the chamber after thecooling operation is completed. The reactive gas may comprise O₂. Thegas introduced into the chamber in the operation for forming aprotective layer may comprise at least one of N₂, Ar, and He.Specifically, in the operation for forming a protective layer, O₂ gasmay be introduced into the chamber at 0.3 to 2.5 SLM (Standard Liter perMinute). The O₂ gas may be introduced into the chamber at 0.5 to 2 SLM.The operation for forming a protective layer may be performed for 10 to60 minutes. The operation for forming a protective layer may beperformed for 12 to 45 minutes. In such a case, the content of eachelement of the protective layer in the thickness direction may beadjusted to suppress variations in optical properties of the entirephase shift film caused from the formation of the protective layer.

Manufacturing Method of Light Shielding Film

The light shielding film of the embodiment may be formed in contact withthe phase shift film or may be formed in contact with another thin filmplaced on the phase shift film.

The light shielding layer may comprise a lower layer and an upper layerpositioned on the lower layer.

The sputtering process may use DC power or RF power.

In consideration of the composition of the light shielding film, asputtering target and a sputtering gas may be selected during sputteringof the light shielding film. When the light shielding film comprises twoor more layers, the type and flow rate of the sputtering gas appliedduring sputtering for each layer may be applied differently.

In the case of a sputtering target, one target comprising chromium maybe applied, and two or more targets comprising at least one of thetargets comprising chromium may be applied. The target may comprisechromium in an amount of 90 atom % or more. The target may comprisechromium in an amount of 95 atom % or more. The target may comprisechromium in an amount of 99 atom % or more.

The type and flow rate of the sputtering gas may be adjusted inconsideration of the composition of elements constituting each layer ofthe light shielding film, crystal characteristics of the light shieldingfilm, optical properties, and the like.

The sputtering gas may comprise a reactive gas and an inert gas.Depending on the type and content of the reactive gas in the sputteringgas, the optical properties and crystal characteristics of the lightshielding film to be formed may be controlled. The reactive gas maycomprise CO₂, O₂, N₂ and NO₂, and the like. The reactive gas may furthercomprise other gases in addition to the above gas.

Depending on the type and content of the inert gas comprised in thesputtering gas, it is possible to control the crystal characteristics ofthe light shielding film to be formed. The inert gas may comprise Ar,He, Ne, and the like. The inert gas may further comprise other gases inaddition to the above gas.

When the lower layer of the light shielding layer is formed, asputtering gas comprising Ar, N₂, He and CO₂ may be injected into thechamber. Specifically, a sputtering gas in which the sum of the flowrates of CO₂ and N₂ is 40% or more compared to the total flow rate ofthe sputtering gas may be injected into the chamber.

When the upper layer of the light shielding layer is formed, asputtering gas comprising Ar and N₂ may be injected into the chamber.Specifically, a sputtering gas in which a flow rate of N₂ is 30% or morecompared to the total flow rate of the sputtering gas may be injectedinto the chamber.

In such a case, the light shielding film may have desired crystalcharacteristics in the embodiment.

Each gas constituting the sputtering gas may be mixed and injected intothe sputtering chamber. Each gas constituting the sputtering gas may beindividually injected through different inlets in the sputtering chamberfor each type.

A magnet may be disposed at the chamber to control the in-planeuniformity of crystal characteristics and in-plane optical properties ofthe light shielding film to be formed. In detail, by disposing themagnet on the back side of the sputtering target and rotating the magnetat a speed within a range preset in the embodiment, plasma may berelatively uniformly distributed over the target front surface. Wheneach layer of the light shielding film is formed, the magnet may berotated at a speed of 50 to 200 rpm.

In the sputtering process, the T/S distance, which is the distancebetween the target and the substrate, and the angle between the surfaceof the substrate and the surface of the target may be adjusted. Wheneach layer of the light shielding film is formed, the T/S distance maybe 240 to 300 mm The angle between the surface of the substrate and thesurface of the target may be 20 to 30 degrees. In such a case, the filmformation speed of the light shielding film is stably controlled, and anexcessive increase in internal stress of the light shielding film can besuppressed.

In the sputtering process, the rotation speed of the substrate havingthe film-forming target surface can be adjusted. The rotation speed ofthe substrate may be 2 to 50 RPM. The rotation speed of the substratemay be 10 to 40 RPM. When the rotation speed of the substrate isadjusted within this range, the light shielding film may exhibit reduceddimensional variation characteristics in an exposure process for longduration.

In addition, it is possible to adjust the intensity of the electricpower applied to the sputtering target when the light shielding film isformed. A discharge region comprising a plasma atmosphere in the chambermay be formed by supplying electric power to a target located in thesputtering chamber. By adjusting the intensity of the electric power, itis possible to control the plasma atmosphere in the chamber togetherwith controlling magnetic field. Through this, it is possible to controlthe crystal characteristics of the light shielding film formed bysputtering.

The intensity of electric power applied to the sputtering target duringthe formation of the lower layer of the light shielding layer may be 0.5to 2 kW. The intensity of the electric power may be 1.0 to 1.8 kW. Theintensity of the electric power may be 1.2 to 1.5 kW. The intensity ofthe electric power applied to the sputtering target during the formationof the upper layer of the light shielding film may be 1 to 3 kW. Theintensity of the electric power may be 1.3 to 2.5 kW. The intensity ofthe electric power may be 1.5 to 2.0 kW. In such a case, it is possibleto effectively prevent the resolution of the photomask from beingdeteriorated due to the thermal variation of the light shielding film.

A spectroscopic ellipsometer may be installed in the sputteringequipment. Through this, it is possible to control the film formationtime while monitoring the optical properties of the light shielding filmto be formed. The method of measuring the optical properties of thelight shielding film after installing a spectroscopic ellipsometer onthe sputtering equipment when the light shielding film is formed isomitted because it is overlapped with the formation of the phase shiftfilm.

When the lower layer of the light shielding film is formed, sputteringmay be performed until the photon energy of incident light becomes 1.6to 2.2 eV at the point where the phase difference between the P wave andthe S wave of the reflected light measured by a spectroscopicellipsometer is 140°. When the lower layer of the light shielding filmis formed, sputtering may be performed until the photon energy ofincident light becomes 1.8 to 2.0 eV at the point where the phasedifference between the P wave and the S wave of the reflected lightmeasured by a spectroscopic ellipsometer is 140°.

When the upper layer of the light shielding film is formed, sputteringcan be performed until the photon energy of incident light becomes 1.7to 3.2 eV at the point where the phase difference between the P wave andthe S wave of the reflected light measured by a spectroscopicellipsometer is 140°. When the upper layer of the light shielding film30 is formed, sputtering may be performed until the photon energy ofincident light at the point where the phase difference between the Pwave and the S wave of the reflected light measured by a spectroscopicellipsometer is 140° becomes 2.5 to 3.0 eV.

In such a case, the formed light shielding film may be comprised in theblind pattern of the photomask to effectively block the exposure light.

Photomask

FIG. 11 is a sectional view for illustrating a photomask according toanother embodiment. An embodiment is described with reference to theFIG. 11.

A photomask 200 according to another embodiment of the presentapplication comprises a transparent substrate 10; a phase shift film 20disposed on the transparent substrate 10; and a light shielding film 30disposed on at least some of the phase shift film 20.

The photomask 200 is analyzed by normal mode XRD (X-Ray Diffraction).

When the normal mode XRD analysis is performed on the upper surface ofthe phase shift film, the phase shift film has the XRD maximum peak at2θ of 15° to 30°.

When the normal mode XRD analysis is performed on the lower surface ofthe transparent substrate, the transparent substrate has the XRD maximumpeak at 2θ of 15° to 30°.

The AI1 value represented by Equation 1 below is 0.9 to 1.1.

$\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the Equation 1, the XM1 is the maximum value of the measured X-rayintensity when the normal mode XRD analysis is performed on the uppersurface of the phase shift film.

The XQ1 is the maximum value of the measured X-ray intensity when thenormal mode XRD analysis is performed on the lower surface of thetransparent substrate.

The photomask may be manufactured using the blank mask described above.In detail, the photomask may be manufactured by patterning the phaseshift film and the light shielding film of the blank mask.

Descriptions of thermal variation characteristics and optical propertiesof the phase shift film and the light shielding film is overlapped withthe descriptions of the thermal variation characteristics and opticalproperties of the phase shift film and the light shielding film, andthus will be omitted.

A photomask according to another embodiment of the present disclosurecomprises a transparent substrate, a phase shift film disposed on thetransparent substrate, and a light shielding film disposed on the phaseshift film.

In the photomask, when the PE₁ value is 3.0 eV and the PE₂ value is 5.0eV, the photon energy of the incident light at the point where Del_2 is0 expressed by Equation 8 below is 4.0 to 5.0 eV.

$\begin{matrix}{{{Del\_}2} = {\lim\limits_{{\Delta\;{PE}}\rightarrow 0}\left( \frac{\Delta\;{pDPS}}{\Delta\;{PE}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

In the Equation 8,

The pDPS value is, when the upper surface of the phase shift film ismeasured with a spectroscopic ellipsometer by applying an incident angleof 64.5° after the light shielding film is removed from the photomask,the phase difference of the P wave and the S wave if the phasedifference of the P wave and the S wave of the reflected light is 180°or less, or a value obtained by subtracting the phase difference betweenthe P wave and the S wave from 360° if the phase difference of the Pwave and the S wave of the reflected light is more than 180°.

The PE value is the photon energy of the incident light within the rangeof PE₁ to PE₂.

The photomask may be manufactured using the blank mask described above.In detail, the photomask may be manufactured by patterning the phaseshift film and the light shielding film of the blank mask.

A description of the optical properties of the phase shift film and thelight shielding film is overlapped with the description of the opticalproperties of the phase shift film and the light shielding filmdescribed above, and thus will be omitted.

Hereinafter, specific examples will be described in more detail.

Manufacture Example: Formation of Phase shift Film and Light ShieldingFilm

Example 1: A quartz transparent substrate having a width of 6 inches, alength of 6 inches, and a thickness of 0.25 inches was disposed in thechamber of the DC sputtering equipment. The target comprising molybdenumand silicon in an atomic ratio of 1:9 was disposed in the chamber tohave a T/S distance of 255 mm and the angle between the surface of thesubstrate and the surface of the target of 25 degrees. A magnet having amagnetic field of 40 mT was disposed on the rear surface of the target.

After that, a sputtering gas mixed in a ratio of Ar:N₂:He=10:52:38 wasintroduced into the chamber, a sputtering power was applied to be 2.05kW, the magnet was subject to rotate, and thereby a sputtering processwas performed. At this time, the rotation speed of the magnet wasincreased from the initial 100 rpm to a maximum of 155 rpm by 11 rpm perminute. The area in which the film is formed was limited to the area setby the width of 132 mm and the length of 132 mm on the surface of thetransparent substrate. The sputtering process was carried out until thephoton energy of incident light at the point where the Del_1 valuemeasured with a spectroscopic ellipsometer was 0 by applying an incidentangle of 64.5° became 2.0 eV.

After sputtering, the surface of the phase shift film of the blank maskwas exposed to Excimer UV light with a wavelength of 172 nm. At thistime, the optical power of the UV light was increased to a maximum of 9mW/cm² by 3 mW/cm² per minute, and was maintained at 9 mW/cm² power for4 minutes.

Thereafter, the blank mask was introduced into a chamber for a heattreatment process, annealed at 1 Pa, and then cooled naturally. Thetemperature in the heat treatment process was increased from roomtemperature to a maximum of 400° C. by 50° C. per minute, and wasmaintained at the maximum temperature for about 30 minutes. Afternatural cooling, O₂ gas in the chamber for the heat treatment processwas introduced into the chamber at a rate of 1 SLM for 30 minutes. Atthis time, the supply temperature of O₂ was about 300° C.

A light shielding film sputtering process was performed on the surfaceof the phase shift film formed into a film. In detail, a chromium targetand the substrate on which and the phase shift film were formed weredisposed so that the T/S distance in the sputtering chamber was 255 mm,and the angle between the surface of the substrate and the surface ofthe target was 25 degrees. A magnet having a magnetic field of 40 mT wasdisposed on the rear surface of the target.

A sputtering gas having a flow ratio of Ar:N₂:He:CO₂=19:11:34:37 wasinjected in the chamber. After that, the sputtering power is applied tobe 1.35 kW, and the photon energy of incident light at the point wherethe phase difference of reflected light between the P wave and the Swave measured with a spectroscopic ellipsometer is 140° while rotatingthe magnet was applied until the photon energy of incident light became1.8 to 2.0 eV. At this time, the rotation speed of the magnet wasincreased from the initial 100 rpm to a maximum of 155 rpm by 11 rpm perminute.

After the lower layer of the light shielding film was formed, asputtering gas having an in-chamber flow ratio of Ar: N₂=57:43 wasinjected. After that, sputtering power was applied to be 1.85 kW, andsputtering was performed until the photon energy of incident light atthe point where the phase difference of the reflected light between theP wave and the S wave of 140° measured with a spectroscopic ellipsometerbecame 2.75 to 2.95 eV. At this time, the rotation speed of the magnetwas increased from the initial 100 rpm to a maximum of 155 rpm by 11 rpmper minute.

Two samples were totally prepared by applying conditions of the filmformation as described above.

Example 2: The sputtering process was performed under the sameconditions as in Example 1, but a magnet magnetic field of 45 mT wasapplied, and the process progress time was carried out until the photonenergy of incident light at the point where the Del_1 value was 0 became1.89 eV.

Example 3: The sputtering process was performed under the sameconditions as in Example 1, except that the composition of thesputtering gas was changed to have a ratio of Ar:N₂:He=8:58:34.

Example 4: A quartz transparent substrate having a width of 6 inches, alength of 6 inches, and a thickness of 0.25 inches was disposed in thechamber of the DC sputtering equipment. The target comprising molybdenumand silicon in an atomic ratio of 1:9 was disposed in the chamber sothat the T/S distance was 255 mm and the angle between the surface ofthe substrate and the surface of the target was 25 degrees. A magnethaving a magnetic field of 40 mT was disposed on the rear surface of thetarget.

After that, a sputtering gas mixed in a ratio of Ar:N₂:He=9:52:39 wasintroduced into the chamber, and the sputtering process was performed tohave a sputtering power of 2 kw, while rotating the magnet at a speed of150 rpm. The area in which the film is formed was limited to the areaset by the width of 132 mm and the length of 132 mm on the surface ofthe transparent substrate. The sputtering process was performed untilthe photon energy of incident light at the point where the Del_1 valuewas 0 became 2.0 eV.

After sputtering, the surface of the phase shift film of the blank maskwas exposed to Excimer UV light with a wavelength of 172 nm at a powerof 7 mW/cm² for 5 minutes.

After that, the blank mask was introduced into a chamber for a heattreatment process, annealed at 400° C. at 1 Pa for 30 minutes, and thencooled naturally. After natural cooling, O₂ gas in the chamber for theheat treatment process was introduced into the chamber at a rate of 1SLM for 30 minutes. At this time, the supply temperature of O₂ was about300° C.

A light shielding film sputtering process was performed on the surfaceof the phase shift film. Specifically, substrate on which the phaseshift film is formed and the chromium target were disposed in thesputtering chamber, a sputtering gas having a flow ratio ofAr:N₂:He:CO₂=19:11:34:37 was introduced into the chamber, and thesputtering power was applied to be 1.35 kW to perform sputtering.Sputtering was carried out until the photon energy of incident light atthe point where the phase difference of reflected light between the Pwave and the S wave of 140° measured with a spectroscopic ellipsometerbecame 1.9 eV, thereby forming a lower layer of the light shieldingfilm.

Thereafter, sputtering gas having a flow ratio of Ar:N₂=57:43 wasintroduced into the chamber and sputtering was performed by applying asputtering power of 2.75 kW. Sputtering was carried out until the photonenergy of incident light at the point where the phase difference ofreflected light between the P wave and the S wave of 140° measured witha spectroscopic ellipsometer became 2.75 eV, thereby forming an upperlayer of the light shielding film.

Two samples were totally prepared by applying the conditions offilm-formation as described above.

Example 5: The sputtering process was performed under the sameconditions as in Example 4, but a magnetic field of 45 mT was applied,and the process progress time was carried out until the photon energy ofincident light at the point where the Del_1 value was 0 became 1.89 eV.

Example 6: A sputtering process was performed under the same conditionsas in Example 4, except that the composition of the sputtering gas waschanged to a ratio of Ar:N₂:He=8:58:34.

Comparative Example 1: A quartz transparent substrate having a width of6 inches, a length of 6 inches, and a thickness of 0.25 inches wasdisposed in the chamber of the DC sputtering equipment. The targetcomprising molybdenum and silicon in an atomic ratio of 1:9 was disposedin the chamber so that the T/S distance was 255 mm and the angle betweenthe surface of the substrate and the surface of the target was 25degrees. A magnet having a magnetic field of 60 mT was disposed on therear surface of the target.

After that, a sputtering gas mixed in a ratio of Ar:N₂:He=9:52:39 wasintroduced into the chamber, sputtering power was 2 kw, the magnet wasrotated at 100 rpm, and thereby a sputtering process was performed. Thearea in which the film is formed was limited to the area set by thewidth of 132 mm and the length of 132 mm on the surface of thetransparent substrate. The sputtering process was performed until thephoton energy of incident light at the point where the Del_1 value was 0became 2.0 eV. After film formation, UV light treatment and heattreatment were not applied.

A light shielding film sputtering process was performed on the surfaceof the phase shift film. Specifically, the T/S distance in thesputtering chamber was 255 mm, and the substrate on which the phaseshift film were formed and the chromium target were disposed so that theangle between the surface of the substrate and the surface of the targetwas 25 degrees. A magnet having a magnetic field of 60 mT was disposedon the rear surface of the target.

A sputtering gas having a flow ratio of Ar:N₂:He:CO₂=19:11:34:37 wasinjected in the chamber. After that, sputtering power was applied to be1.35 kW, and the photon energy of incident light at the point where thephase difference of reflected light between the P wave and the S wave of140° measured with a spectroscopic ellipsometer became 1.8 to 2.0 eV. Atthis time, the rotation speed of the magnet was 100 rpm.

After the lower layer of the light shielding film was formed, asputtering gas having an in-chamber flow rate ratio of Ar:N₂=57:43 wasinjected. After that, sputtering power was applied to be 1.85 kW, andsputtering was performed until the photon energy of incident light atthe point where the phase difference of reflected light between the Pwave and the S wave of 140° measured with a spectroscopic ellipsometerbecame 2.75 to 2.95 eV while rotating the magnet.

Comparative Example 2: A sputtering process was performed under the sameconditions as in Comparative Example 1, but a magnet magnetic field of20 mT was applied. In addition, no additional heat treatment process wasapplied.

Comparative Example 3: A quartz transparent substrate having a width of6 inches, a length of 6 inches, and a thickness of 0.25 inches wasdisposed in the chamber of the DC sputtering equipment. The targetcomprising molybdenum and silicon in an atomic ratio of 1:9 was placedin the chamber so that the T/S distance was 255 mm and the angle betweenthe substrate and the target was 25 degrees. A magnet having a magneticfield of 60 mT was disposed on the rear surface of the target.

After that, a sputtering gas mixed in a ratio of Ar:N₂:He=9:52:39 wasintroduced into the chamber, and the sputtering process was performedwhile rotating the magnet at a speed of 100 rpm with a sputtering powerof 2 kW. The area in which the thin film was formed was limited to thearea set by the width of 132 mm and the length of 132 mm on the surfaceof the transparent substrate. The sputtering process was performed untilthe photon energy of incident light at the point where the Del_1 valuewas 0 became 2.0 eV. No additional UV light treatment and heat treatmentwere applied.

A light shielding film sputtering process was performed on the surfaceof the phase shift film formed into a film. Specifically, after thesubstrate on which the phase shift film was formed and the chromiumtarget were disposed in the sputtering chamber, a sputter gas having aflow ratio of Ar:N₂:He:CO₂=19:11:34:37 was introduced into the chamber,and the sputtering power was applied to be 1.35kw, thereby performingsputtering. Sputtering was carried out until the photon energy ofincident light at the point where the phase difference of reflectedlight between the P wave and the S wave of 140° measured with aspectroscopic ellipsometer reached 1.9 eV, thereby forming a lightshielding film lower layer.

After that, sputtering gas having a flow ratio of Ar:N₂=57:43 wasintroduced into the chamber and sputtering was performed by applying2.75 kW of sputtering power. Sputtering was carried out until the photonenergy of incident light at the point where the phase difference ofreflected light between the P wave and the S wave of 140° measured witha spectroscopic ellipsometer became 2.75 eV, thereby forming a lightshielding film lower layer.

Comparative Example 4: A sputtering process was performed under the sameconditions as in Comparative Example 3, but a magnet magnetic field of20 mT was applied, and the composition of the sputtering gas was changedto have a ratio of Ar:N₂:He=8:58:34 in the sputtering process for thephase shift film.

For the samples of Examples 1 to 3 and Comparative Examples 1 and 2, theDel_1 value distribution was measured using a spectroscopic ellipsometer(MG-PRO product available from NANO-VIEW) installed in a sputteringdevice before the formation of the light shielding film. Specifically,after setting the angle of incident light to be 64.5 with respect to thesurface of the phase shift film on which the film formation has beencompleted for each Example and Comparative Example, the phase differencebetween P and S waves of reflected light according to photon energy ofincident light of incident light was measured and calculated into aDel_1 value. The measurement results of the parameters related to Del_1value were shown in Table 2 below.

Evaluation Example: XRD Analysis

Normal mode XRD analysis and fixed mode XRD analysis were performed onthe lower surface of the transparent substrate of the samples ofExamples 1 to 3, Comparative Examples 1 and 2, and normal mode XRDanalysis and fixed mode XRD analysis were performed on the upper surfaceof the light shielding film of the samples. Thereafter, the lightshielding film comprised in the sample was removed by etching andcleaning processes to expose the upper surface of the phase shift film.

Normal-mode XRD analysis and fixed-mode XRD analysis were performed onthe exposed surface of the phase shift film.

The normal mode XRD analysis was performed under the followingconditions.

Equipment name: Rigaku smartlab

x-ray source: Cu target

x-ray information: wavelength 1.542 nm, 45 kV, 200 mA

(Θ-2Θ) measurement range: 10-100°

Step: 0.05°

Speed: 5°/min

The fixed mode XRD analysis was performed under the followingconditions.

Equipment name: Rigaku smartlab

x-ray source: Cu target

x-ray information: wavelength 1.542 nm, 45 kV, 200 mA

X-ray generator exit angle: 1°

(Θ-2Θ) measurement range: 10-100°

Step: 0.05°

Speed: 5°/min

The measurement results for each Example and Comparative Example wereshown in Table 1 below.

Evaluation Example: Del_1 Value Measurement

The light shielding film was removed from the samples of Examples 4 to 6and Comparative Examples 3 and 4 through etching. Specifically, aftereach sample was placed in the chamber, an etching process was performedby supplying a chlorine-based gas as an etchant to remove the lightshielding film.

Thereafter, the Del_1 value distribution when PE₁ was 1.5 eV and PE₂ was5.0 eV was measured for the sample using a spectroscopic ellipsometer(manufactured by MG-PRO, Nano-View) installed in a sputtering device.Specifically, after setting the angle of incident light to 64.5 withrespect to the surface of the phase shift film on which the filmformation has been completed for each Example and Comparative Example,the phase difference between P and S waves of reflected light accordingto photon energy of incident light was measured and calculated into aDel _1 value.

The parameters related to the distribution of the Del_1 measured foreach sample were shown in Table 2 below. Graphs showing the distributionof DPS and Del_1 measured for each sample were shown in FIGS. 12 to 21.

Evaluation Example: Phase difference, Transmittance Measurement

For the samples of examples and comparative examples described above,the light shielding film was removed by etching in the same manner as inthe XRD analysis method. The phase difference and transmittance weremeasured using a phase difference/transmittance measuring instrument(MPM193 manufactured by Lasertec). Specifically, by using an ArF lightsource (wavelength 193 nm) to irradiate light to the region where thephase shift film was formed and the region where the phase shift filmwas not formed of each sample, the phase difference and transmittancedifference values between both regions were measured and calculated.Therefore, it was described in Table 3 below.

Evaluation Example: Contrast and CD Value Measurement

After a photoresist film was formed on the surface of the phase shiftfilm of each sample in Examples and Comparative Examples, a denserectangular pattern was exposed on the surface of the photoresist filmusing Nuflare's EBM 9000 model. The target CD value of the squarepattern was set to 400 nm (4×). After a pattern on the photoresist filmof each sample was developed, the light shielding film and the phaseshift film were etched according to the developed pattern shape usingthe Tetra X model of Applied Materials. Thereafter, the photoresistpattern was removed and then photomask made from each sample in Exampleand Comparative Examples was manufactured.

Transferring pattern on a surface of wafer through the exposure processapplied to the photomask of each sample. Contrast values and normalizedCD values of the transferred pattern were measured and calculated usingthe AIMS 32 model of Carl Zeiss. For measurement and calculation, thenumerical aperture (NA) was set to 1.35, the illumination system was setto crosspole of 30×, outer sigma of 0.8, and in/out sigma ratio of 85%.The measured data were shown in Table 3 below.

Evaluation Example: Measurement and Evaluation of Content of EachElement in the Thickness Direction of Protective Layer

For the samples of Examples 4 to 6 and Comparative Examples 3 and 4, thecontent of each element in the thickness direction of the protectivelayer was measured. Specifically, using Thermo Scientific's K-alphamodel, the analyzer type/channel of 180 degree double focusinghemispherical analyzer/120 channel, the X-ray light source of Al Kamicro-focused, the power of 1 keV, the working pressure of 1E-7 mbar,and a gas of Ar were applied and thereby the content of each element inthe thickness direction of the protective layer was measured.

As a result of the measurement, when the protective layer comprised aregion in which the ratio of nitrogen content to oxygen content in thethickness direction was 0.4 to 2 and the region had a thickness of 30 to80% compared to a total thickness of the protective layer, it wasevaluated as O, and when the region had a thickness of less than 30% ormore than 80% compared to a total thickness of the layer, it wasevaluated as X. The measurement results were shown in Table 3 below.

TABLE 1 AI1 AI2 AI3 AI4 AI5 AI6 Example 1 1.00 1.02 1.01 0.99 0.961.0938 Example 2 1.01 1.02 1.02 0.99 0.95 1.10 Example 3 1.00 1.03 1.021.00 0.93 1.11 Example 4 — — — — — — Example 5 — — — — — — Example 6 — —— — — — Comparative 0.97 0.96 0.94 1.05 0.99 1.05 Example 1 Comparative0.94 0.95 0.93 1.02 0.98 1.05 Example 2 Comparative — — — — — — Example3 Comparative — — — — — — Example 4

TABLE 2 Photon Energy of Photon incident Energy of light at the incidentAverage Point where light at the Average Average Value of Maximum, Del_1value Point where Value of Value of Del_1 when Value of Del_1 is 0 whenDel_1 is 0 Del_1 when Del_1 when PE₁ is B* when PE₁ is PE₁ is 1.5 eVwhen PE₁ is PE₁ is 1.5 eV PE₁ is S* and PE₂ is 1.5 eV and PE₂ and PE₂ is3 eV and PE₂ and PE₂ is and PE₂ is 5 eV is 5 eV 3 eV (eV) is 5 eV(eV) S*(°/eV) B* (°/eV) (°/eV) (°/eV) Example 1 2.00 4.44 — — — — Example 21.89 4.31 — — — — Example 3 2.09 4.65 — — — — Example 4 2.02 4.46 86.5−57.3 91.6 157.5 Example 5 1.95 4.28 82.1 −58.5 102.2 187.3 Example 62.09 4.58 94.2 −57.0 84.0 143.7 Comparative 1.65 3.84 — — — — Example 1Comparative 2.17 4.80 — — — — Example 2 Comparative 1.71 3.79 75.0 −66.8−21.8 320.0 Example 3 Comparative 2.15 4.65 98.3 −53.5 58.1 103.5Example 4 *S* means the minimum value among Photon energies of incidentlight in a point having the Del_2 value of 0. *B* means the maximumvalue among Photon energies of incident light in a point having theDel_2 value of 0.

TABLE 3 Content Evaluation of Each Element in Transmittance PhaseNormalized the Thickness (%) difference (°) Contrast Normalized CDDirection Example 1 6.1 178.5 1.000 0.99 — Example 2 5.4 186.1 0.9891.01 — Example 3 6.9 172.4 0.959 1.03 — Example 4 6.1 175.7 1.000 1.00 ◯Example 5 5.6 181.0 0.992 1.01 ◯ Example 6 6.4 172.6 0.977 1.02 ◯Comparative 3.4 209.1 0.929 1.06 — Example 1 Comparative 7.8 166.0 0.8831.10 — Example 2 Comparative 3.3 205.3 0.918 1.05 X Example 3Comparative 7.4 162.0 0.895 1.08 X Example 4

In the Table 1, the AI1, AI2, AI3, and AI4 values of Examples 1 to 3were measured to be closer to 1 compared to Comparative Examples 1 and2.

In the Table 3, the transmittance of Examples 1 to 6 was within therange of 5.4 to 6.9%, and the phase difference was within the range of170 to 190°, but Comparative Examples 1 and 3 had transmittance lessthan 4%, and the phase difference was measured to be 200° or more andComparative Examples 2 and 4 had transmittance of 7.4% or more anddifference of less than 170°.

In the evaluation of the content of each element in the thicknessdirection of the protective layer, Examples 4 to 6 were evaluated as O,whereas Comparative Examples 3 and 4 were evaluated as X.

Examples 1 to 6 showed a normalized contrast of 0.95 or more and anormalized CD value of 1.03 or less, whereas Comparative Examples 1 to 4showed a normalized contrast of less than 0.93 and a normalized CD valueof 1.06 or more.

Although the preferred embodiment has been described in detail above,the scope of the present application is not limited thereto, and variousmodifications and improvements by those skilled in the art using thebasic concept of the embodiment defined in the following claims are alsowithin the scope of the present application.

DESCRIPTION OF FIGURE NUMBERS

100: blank mask

10: transparent substrate

20: phase shift film 21: phase difference adjustment layer 22:protective layer

30: light shielding film

60: X-ray generator

70: detector

80: sample

200: photomask

TA: Transmissive portion

NTA: semi-transmissive portion

θ: angle of incidence N: normal line

Li: incident light Lr: reflected light

P: P wave component of incident light S: S wave component of incidentlight

P′: P wave component of reflected light S′: S wave component ofreflected light

Δ: phase difference between P wave and S wave of reflected light

What is claimed is:
 1. A blank mask comprising: a transparent substrate;a phase shift film disposed on the transparent substrate; and a lightshielding film disposed on at least some of the phase shift film;wherein the blank mask is analyzed by normal mode XRD (X-RayDiffraction), wherein the phase shift film has a XRD maximum peak at 2θof 15° to 30° when the normal mode XRD analysis is performed on an uppersurface of the phase shift film, wherein the transparent substrate has aXRD maximum peak at 2θ of 15° to 30° when the normal mode XRD analysisis performed on a lower surface of the transparent substrate, andwherein the blank mask has AI1 value of 0.9 to 1.1 expressed by Equation1 below; $\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$ where in the Equation 1, the XM1 is a maximum value of themeasured X-ray intensity when the normal mode XRD analysis is performedon the upper surface of the phase inversion film, and the XQ1 is amaximum value of the measured X-ray intensity when the normal mode XRDanalysis is performed on the lower surface of the transparent substrate.2. The blank mask of claim 1, which is analyzed by fixed mode XRD,wherein the phase shift film has a first peak, which is the XRD maximumpeak at 2θ of 15° to 25° when the fixed mode XRD analysis is performedon the upper surface of the phase shift film, wherein the transparentsubstrate has a second peak, which is the XRD maximum peak at 2θ of 15°to 25° when the fixed mode XRD analysis is performed on the lowersurface of the transparent substrate, and wherein AI2 value expressed byEquation 2 below is 0.9 to 1.1; $\begin{matrix}{{{AI}\; 2} = \frac{{XM}\; 2}{{XQ}\; 2}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$ wherein the Equation 2, the XM2 is the intensity value ofthe first peak, and the XQ2 is the intensity value of the second peak.3. The blank mask of claim 1, wherein A13 value expressed by Equation 3below is 0.9 to 1.1; $\begin{matrix}{{{AI}\; 3} = \frac{{AM}\; 1}{{AQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$ wherein the Equation 3, the AM1 is an area of the regionwhere 2θ is 15° to 30° in the X-ray intensity graph measured when normalmode XRD analysis is performed on the upper surface of the phaseinversion film, and the AQ1 is an area of the region where 2θ is 15° to30° in an X-ray intensity graph measured when normal mode XRD analysisis performed on the lower surface of the transparent substrate.
 4. Theblank mask of claim 3, wherein AI4 value expressed by Equation 4 belowis 0.9 to 1.1; $\begin{matrix}{{{AI}\; 4} = \frac{{XM}\; 4}{{XQ}\; 4}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$ wherein the Equation 4, the XM4 is the X-ray intensitywhere 2θ is 43° when the normal mode XRD analysis performed on the uppersurface of the phase inversion film, and the XQ4 is the X-ray intensitywhere 2θ is 43° when the normal mode XRD analysis performed on the lowersurface of the transparent substrate.
 5. The blank mask of claim 1,wherein a photon energy of incident light at the point where the Del_1value according to Equation 7 below is 0 is 1.8 to 2.14 eV when PE₁ is1.5 eV and PE₂ is 3 eV; $\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta PE}\rightarrow 0}\left( \frac{\Delta DPS}{\Delta PE} \right)}} & \left\lbrack {{Equation}\mspace{11mu} 7} \right\rbrack\end{matrix}$ wherein the Equation 7, the DPS value is a phasedifference between the P wave and the S wave of reflected light if thephase difference between the P wave and the S wave of the reflectedlight is 180° or less or a value obtained by subtracting the phasedifference between the P wave and the S wave of the reflected light from360° if the phase difference between the P wave and the S wave of thereflected light is more than 180°, when the phase shift film is measuredwith a spectroscopic ellipsometer by applying an incident angle of64.5°, and the PE value is the photon energy of the incident lightwithin the range of the PE₁ value to the PE₂ value.
 6. The blank mask ofclaim 1, wherein the photon energy of incident light at the point wherethe Del_1 value according to Equation 7 below is 0 is 3.8 to 4.64 eVwhen the PE₁ value is 3.0 eV and the PE₂ value is 5.0 eV;$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta PE}\rightarrow 0}\left( \frac{\Delta DPS}{\Delta PE} \right)}} & \left\lbrack {{Equation}\mspace{11mu} 7} \right\rbrack\end{matrix}$ where in the Equation 7, the DPS value is the phasedifference between the P wave and the S wave of reflected light if thephase difference between the P wave and the S wave of the reflectedlight is 180° or less, or a value obtained by subtracting the phasedifference between the P wave and the S wave of the reflected light from360° if the phase difference between the P wave and the S wave of thereflected light is more than 180°, when the phase shift film is measuredwith a spectroscopic ellipsometer by applying an incident angle of64.5°, and the PE value is the photon energy of the incident lightwithin the range of the PE₁ value to the PE₂ value.
 7. A blank maskcomprising: a transparent substrate; a phase shift film disposed on thetransparent substrate; and a light shielding film disposed on the phaseshift film; wherein the blank mask has the photon energy of the incidentlight at the point where Del_1 expressed by Equation 7 below is 0 is 3.8to 4.64 eV, when the PE₁ value is 3.0 eV and the PE₂ value is 5.0 eV;$\begin{matrix}{{{Del\_}1} = {\lim\limits_{{\Delta PE}\rightarrow 0}\left( \frac{\Delta DPS}{\Delta PE} \right)}} & \left\lbrack {{Equation}\mspace{11mu} 7} \right\rbrack\end{matrix}$ where in the Equation 7, the DPS value is, after removingthe light shielding film from the blank mask, the phase differencebetween the P wave and the S wave of reflected light if the phasedifference between the P wave and S wave of the reflected light is 180°or less, or a value obtained by subtracting the phase difference betweenthe P wave and the S wave of the reflected light from 360° if the phasedifference between the P wave and the S wave of the reflected light ismore than 180° when the surface of the phase shift film is measured witha spectroscopic ellipsometer by applying an incident angle of 64.5°, andthe PE value is the photon energy of the incident light within the rangeof PE₁ to PE₂.
 8. The blank mask of claim 7, wherein the photon energyof the incident light at the point where the Del_1 value is 0 is 1.8 to2.14 eV, when the PE₁ value is 1.5 eV and the PE₂ value is 3.0 eV. 9.The blank mask of claim 7, wherein the average value of the Del_1 is 78to 98°/eV, when the PE₁ value is 1.5 eV and the PE₂ value is the minimumvalue within photon energy values of incident light at the point wherethe Del_1 value is
 0. 10. The blank mask of claim 7, wherein the averagevalue of the Del_1 is −65 to −55°/eV, when the PE₁ value is the minimumvalue within photon energy values of the incident light at the pointwhere the Del_1 value is 0, and the PE₂ value is the maximum valuewithin the photon energy values of the incident light at the point wherethe Del_1 value is
 0. 11. The blank mask of claim 7, wherein the averagevalue of the Del_1 is 60 to 120°/eV, when the PE₁ value is the maximumvalue within photon energy values of incident light at a point where theDel_1 value is 0, and when the PE₂ value is 5.0 eV.
 12. The blank maskof claim 7, wherein the maximum value of the Del_1 value is 105 to300°/eV, when the PE₁ value is 1.5 eV and the PE₂ value is 5.0 eV. 13.The blank mask of claim 12, wherein the photon energy of the incidentlight at the point where the maximum value of the Del_1 value is 4.5 eVor more.
 14. The blank mask of claim 1, wherein the phase shift filmcomprises a phase difference adjustment layer and a protective layerdisposed on the phase difference adjustment layer, and wherein the phaseshift film comprises a transition metal, silicon, oxygen and nitrogen,wherein the phase difference adjustment layer comprises nitrogen in anamount of 40 to 60 atom %, wherein the protective layer comprisesnitrogen in an amount of 20 to 40 atom %, and wherein the protectivelayer comprises a region in which the ratio of nitrogen content tooxygen content in the thickness direction is 0.4 to 2, and the regionhas a thickness of 30 to 80% compared to a total thickness of theprotective layer.
 15. A photomask comprising: a transparent substrate; aphase shift film disposed on the transparent substrate; and a lightshielding film disposed on at least some of the phase shift film,wherein the photomask is analyzed by normal mode XRD, wherein the phaseshift film has a XRD maximum peak at 20 of 15° to 30° when normal modeXRD analysis is performed on an upper surface of the phase shift film,wherein the transparent substrate has a XRD maximum peak at 20 of 15° to30° when the normal mode XRD analysis is performed on a lower surface ofthe transparent substrate, and wherein the blank mask has AI1 value of0.9 to 1.1 expressed by Equation 1 below is; $\begin{matrix}{{{AI}\; 1} = \frac{{XM}\; 1}{{XQ}\; 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$ where in the Equation 1, the XM1 is the maximum value ofthe measured X-ray intensity when the normal mode XRD analysis isperformed on the phase shift film, and the XQ1 is the maximum value ofthe measured X-ray intensity when the normal mode XRD analysis isperformed on the lower surface of the transparent substrate.